# Where births are falling: report

Chapter 2.4 of ZIP Code Destiny, by Vishal Singh (NYU Stern). Generated from the chapter's data files; the reading version is at https://vishalsingh.org/zipcode/where-births-are-falling. Table n of this report is figure n of the chapter.

## Identification

- Title: Where births are falling
- Label: The vanishing cradle
- Chapter: 2.4 (Part II, Birth; An American life)
- Question: Which counties lost the most births between 2018 and 2024, and how did the age of mothers change in those places?
- Dek: Births in the counties that CDC WONDER identifies fell 4.6% from 2018 to 2024, by 5.6% in the least deprived quartile of counties and 7.3% in the most deprived.
- Grain: counties
- Status: published
- Published: 2026-10-09
- Updated: not revised
- Data sources:
  - CDC WONDER natality. CDC WONDER natality, county totals and county by mother's age, births in 2018 to 2024 (consolidated pulls); 2024 is final; years: 2018-2024; weights: births in each county (pooled ratios of sums); changes and shares pooled over counties
  - Area Deprivation Index. Neighborhood Atlas Area Deprivation Index 2023 (v4.0.1), tract national rank, averaged to counties with 2019-2023 tract population; years: 2023 release (version 4.0.1; built on ACS 2019-2023); weights: 2019-2023 tract population
- Canonical URL: https://vishalsingh.org/zipcode/where-births-are-falling
- Report: https://vishalsingh.org/zipcode/where-births-are-falling/report
- Markdown: https://vishalsingh.org/zipcode/where-births-are-falling/report.md
- BibTeX key: singh2026wherebirthsarefalling

```bibtex
@misc{singh2026wherebirthsarefalling,
  author = {Singh, Vishal},
  title = {Where births are falling},
  year = {2026},
  url = {https://vishalsingh.org/zipcode/where-births-are-falling},
  note = {In ZIP Code Destiny. Published 9 October 2026.}
}
```

## Principal estimates

The facts the dek and the opening prose cite, in order of appearance.

| Estimand | Population | Period | Value | Interval | n | Weights | Source | Fact id |
| --- | --- | --- | ---: | --- | ---: | --- | --- | --- |
| fall in the count of births from 2018 to 2024 | live births in the counties that CDC WONDER natality identifies in every year (counties with 100,000 or more residents in the population vintage WONDER uses) | 2018 to 2024 | 4.6% |   |   | none (full count) | CDC WONDER natality | decline_named |
| fall in the pooled count of births from 2018 to 2024, bootstrap interval over counties | live births in the least deprived quartile of the named counties by county Area Deprivation Index rank | births in 2018 and 2024 | 5.6% | 95% CI 2.8% to 8.2% | 144 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality | decline_q1 |
| fall in the pooled count of births from 2018 to 2024, bootstrap interval over counties | live births in the most deprived quartile of the named counties by county Area Deprivation Index rank | births in 2018 and 2024 | 7.3% | 95% CI 5.8% to 8.8% | 145 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality | decline_q4 |
| count of counties | counties that WONDER natality identifies in every year from 2018 to 2024 and that have births | births in 2018 to 2024 | 578 |   |   | none (full count) | CDC WONDER natality | counties_used |
| count of live births | live births in the counties that CDC WONDER natality identifies in every year (counties with 100,000 or more residents in the population vintage WONDER uses) | 2018 | 3.02 million |   |   | none (full count) | CDC WONDER natality | births_named_2018 |
| count of live births | live births in the counties that CDC WONDER natality identifies in every year (counties with 100,000 or more residents in the population vintage WONDER uses) | 2024 | 2.88 million |   |   | none (full count) | CDC WONDER natality | births_named_2024 |
| population size at which WONDER identifies a county, applied to an earlier population vintage than the 2020 census (a definition) | counties that CDC WONDER natality identifies | births in 2018 to 2024 | 100,000 |   |   | none (definition) | CDC WONDER natality | wonder_threshold |
| share of births in the named counties | live births in the 50 states and DC | 2024 | 79.4% |   |   | none (full count) | CDC WONDER natality | share_named_2024 |
| pooled change in the count of births from 2018 to 2024, bootstrap interval over counties | live births in the named counties in the Census South region | births in 2018 and 2024 | 0.0% | 95% CI −1.7% to 1.8% | 232 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality | region_south |
| pooled change in the count of births from 2018 to 2024, bootstrap interval over counties | live births in the named counties in the Census Midwest region | births in 2018 and 2024 | −8.4% | 95% CI −10.4% to −6.3% | 137 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality | region_midwest |
| pooled change in the count of births from 2018 to 2024, bootstrap interval over counties | live births in the named counties in the Census West region | births in 2018 and 2024 | −7.9% | 95% CI −10.7% to −5.0% | 99 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality | region_west |
| pooled change in the count of births from 2018 to 2024, bootstrap interval over counties | live births in the named counties in the Census Northeast region | births in 2018 and 2024 | −5.0% | 95% CI −7.3% to −2.5% | 110 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality | region_northeast |
| fall in the pooled count of births from 2018 to 2024, bootstrap interval over counties | live births in the second quartile of the named counties by county Area Deprivation Index rank | births in 2018 and 2024 | 2.6% | 95% CI −0.6% to 5.3% | 145 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality | decline_q2 |
| fall in the pooled count of births from 2018 to 2024, bootstrap interval over counties | live births in the third quartile of the named counties by county Area Deprivation Index rank | births in 2018 and 2024 | 3.1% | 95% CI 1.6% to 4.5% | 144 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality | decline_q3 |
| pooled change in the count of births from 2018 to 2024, bootstrap interval over counties | live births to mothers aged 15 to 19 in the named counties that publish the band in both years | births in 2018 and 2024 | 24.6% | 95% CI 22.7% to 26.5% | 577 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality | fall_1519 |
| age-of-mother range used in this chapter, from WONDER's five-year bands (a definition) | mothers | all years (a definition) | 15 to 19 |   |   | none (definition) | CDC WONDER natality | band_1519 |
| pooled change in the count of births from 2018 to 2024, bootstrap interval over counties | live births to mothers aged 40 to 44 in the named counties that publish the band in both years | births in 2018 and 2024 | 19.5% | 95% CI 17.0% to 22.3% | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality | rise_4044 |
| age-of-mother range used in this chapter, from WONDER's five-year bands (a definition) | mothers | all years (a definition) | 40 to 44 |   |   | none (definition) | CDC WONDER natality | band_4044 |

## Findings

Births in the 578 counties that CDC WONDER identifies fell from 3.02 million in 2018 to 2.88 million in 2024, a decline of 4.6%. These counties have 100,000 or more residents in the population vintage WONDER uses, and they record 79.4% of the births in the United States in 2024.

Pooled over counties, births changed by 0.0% (95% CI −1.7% to 1.8%) in the South, −8.4% (95% CI −10.4% to −6.3%) in the Midwest, −7.9% (95% CI −10.7% to −5.0%) in the West and −5.0% (95% CI −7.3% to −2.5%) in the Northeast. Pooled births fell by 5.6% (95% CI 2.8% to 8.2%) in the least deprived quartile of these counties, by 2.6% and 3.1% in the second and third quartiles, and by 7.3% (95% CI 5.8% to 8.8%) in the most deprived. The losses do not rise in steps with deprivation, and region and deprivation overlap, so the chapter looks at them together.

The ages of mothers shifted too. Between 2018 and 2024 births fell by 24.6% among mothers aged 15 to 19 and rose by 19.5% among mothers aged 40 to 44.

Everything in this chapter is a count of births in a county or a share of those births. A birth rate divides births by the women who could have had them, and the files behind this book have no county counts of women by age, so the chapter reports counts and shares and no rates. The babies in these counties are the subject of Chapter 2.1, Birthweight and preterm birth (https://vishalsingh.org/zipcode/birthweight-and-preterm-birth), which asks how heavy they were at birth, and of Chapter 2.2, Infant mortality (https://vishalsingh.org/zipcode/infant-mortality), which follows them through the first year.

### Births have not returned to their 2018 level

Births in the named counties fell from 2018 to 2020 and rose through 2022 (Table 1). They fell again to a low in 2023, when they were 5.5% below 2018, and rose 0.9% in 2024. In 2020 they were 4.8% below 2018, and by 2024 they were still 4.6% below.

WONDER pools the births of every smaller county in a state into one row, 49 rows in all. Those rows record 0.77 million births in 2018 and 0.75 million in 2024, a decline of 3.0%, so the named counties lost a larger share of their births than the rest of the country combined. Across the whole country births fell from 3.79 million to 3.63 million, a decline of 4.3%. The count for 2024 is the one in the final report of the National Center for Health Statistics, and 2024 is final in these data.[1]

Birth rates in the United States have been falling since the Great Recession. Kearney, Levine and Pardue document that birth rates fell between 2007 and 2020 across many groups of women, and they find that the recession explains only part of the early decline.[2] This chapter starts in 2018 and describes where the recent loss fell.

Table 1. Births in the named counties fell 4.6% from 2018 to 2024 with a low in 2023, a larger fall than the 3.0% in all other counties

The 578 named counties are the counties that WONDER identifies in every year from 2018 to 2024 and that have births in every year. WONDER lists two more county identifiers in every year, Cape May County, New Jersey, and Portsmouth city, Virginia. It gives them no births because it folded them into their state's pooled row, so they are left out. Every named county appears in every year from 2018 to 2024, so no county drops out of the panel by entering or leaving WONDER's list.

The selection is by size as WONDER measured it. WONDER applies its threshold of 100,000 residents to an earlier population estimate than the 2020 Census. By 2020 Census population, 27 counties outside Connecticut that have 100,000 or more residents are still in the pooled rows, among them Sumter County, Florida, Gallatin County, Montana, and Flagler County, Florida. In the other direction, one named county, Ashtabula County, Ohio, is below the line. The staged atlas has no 2020 count for Connecticut, whose counties are all named. Counties that grew past the line after WONDER's estimate therefore sit in the pooled rows. The comparison of the 3.0% decline there with the 4.6% decline in the named counties compares two groups defined by an earlier population estimate and not by size today.

The named counties record 79.7% of births in 2018 and 79.4% in 2024, and the smallest of them recorded at least 613 births in every year. County results in this chapter describe these counties and not the country. The pooled rows lost fewer births, with the caveat that they include counties that now exceed the line.

### Births held up in the South and fell elsewhere

The Census Bureau groups states into the Northeast, the Midwest, the South and the West. The South, which has 16 states and the District of Columbia, holds 232 of the named counties, or 40.1%. Pooled over its counties, the South's births changed by 0.0% (95% CI −1.7% to 1.8%) from 2018 to 2024, an interval that includes zero. Births in the Midwest changed by −8.4% (95% CI −10.4% to −6.3%), in the West by −7.9% (95% CI −10.7% to −5.0%) and in the Northeast by −5.0% (95% CI −7.3% to −2.5%), so the intervals for those three regions lie below zero.

The South's change is higher than the Northeast's by 5.0 percentage points (95% CI 2.0 percentage points to 7.9 percentage points), than the Midwest's by 8.4 percentage points (95% CI 5.7 percentage points to 11.1 percentage points) and than the West's by 7.9 percentage points (95% CI 4.3 percentage points to 11.3 percentage points). The intervals come from a bootstrap that resamples whole counties, so they show how much a region's pooled change depends on which counties it holds.

Table 2. Of the 58 counties with the largest gains in births, 43 are in the South, which holds 40.1% of the named counties

The map (Table 2) shows the same split county by county. The top tenth of counties by change, with gains of 10.2% or more, holds 58 counties, and 43 of them are in the South. The bottom tenth, with declines of 13.6% or more, holds 58 counties, and 13 are in the South.

Counted one county at a time, 65.7% of the named counties lost births. Births were lower in 2024 than in 2018 in 380 counties, higher in 197 and the same in one.

The median county lost 3.8%, and from the 5th to the 95th percentile of counties, changes run from a decline of 16.5% to a gain of 19.9%. The pooled decline of 4.6% is larger than the median county's because the pooled figure weights each county by its births and the median counts each county once.

Table 3. The ten largest gains in births are all in the South, and the ten largest declines are spread across every Census region

Table 3 lists the ten counties with the largest gains and the ten with the largest declines. Beyond the middle of the distribution, where changes from the 5th to the 95th percentile of counties run from a decline of 16.5% to a gain of 19.9%, the extremes are a decline of 23.9% in St. Louis city, Missouri, and a gain of 67.6% in Kaufman County, Texas. All of the gains are in the South, in Texas, North Carolina and Georgia. The declines are spread across every region and include St. Louis city, Missouri, Hinds County, Mississippi, Humboldt County, California, San Francisco County and Orleans Parish, Louisiana. Every county listed had at least 987 births in 2018. Small counts move more from year to year by chance, so the order within each group is less stable than the groups themselves.

A county's births change when women have fewer children, when the number of women of childbearing age changes, or both, and these data cannot separate them. WONDER places a birth in the mother's county of residence, so a county that adds young families counts their births, and a gain in a fast-growing county may reflect arrivals as much as larger families.

### The most deprived counties lost more births than the middle quartiles

To place counties on a deprivation scale, each census tract carries its Area Deprivation Index national rank, which orders neighborhoods by deprivation, with a higher rank meaning more deprived.[3] A tract's rank is the unweighted mean of the ranks of its block groups, and a county's rank is the average of its tracts' ranks, weighted by tract population, the measure used in Chapter 2.1, Birthweight and preterm birth (https://vishalsingh.org/zipcode/birthweight-and-preterm-birth). Quartiles hold equal numbers of the named counties, so the most deprived quartile is relative to large counties and not to the nation.

By 2024 pooled births in the most deprived quartile were 7.3% (95% CI 5.8% to 8.8%) below 2018 (Table 4). All four quartiles fell to 2020. In 2021 births in the other three quartiles rose and births in the most deprived quartile did not. Its pooled change was −0.3% (95% CI −0.8% to 0.1%), an interval that includes zero, and the other quartiles rose by more, by 1.9 percentage points (95% CI 1.0 percentage points to 3.0 percentage points) in the least deprived quartile, 2.5 percentage points (95% CI 1.4 percentage points to 3.6 percentage points) in the second and 1.3 percentage points (95% CI 0.5 percentage points to 2.2 percentage points) in the third.

The second and third quartiles lost 2.6% (95% CI −0.6% to 5.3%) and 3.1% (95% CI 1.6% to 4.5%) from 2018 to 2024, and the middle quartiles together lost 2.8% (95% CI 1.1% to 4.5%). The most deprived quartile therefore lost 4.5 percentage points (95% CI 2.3 percentage points to 6.7 percentage points) more than the middle quartiles. The least deprived quartile lost 5.6% (95% CI 2.8% to 8.2%). It lost 2.7 percentage points (95% CI −0.5 percentage points to 5.9 percentage points) more than the middle quartiles and 1.7 percentage points (95% CI −1.2 percentage points to 5.0 percentage points) less than the most deprived quartile, and both intervals include zero, so the data do not place it with either.

A single slope does not summarize the pattern. Regressing each county's change on its deprivation rank gives +0.5 percentage points (95% CI −0.2 percentage points to 1.2 percentage points) per ten ranks when counties are weighted by their births and −0.7 percentage points (95% CI −1.1 percentage points to −0.3 percentage points) when each county counts once. The sign depends on the weights, and only the unweighted interval excludes zero.

Table 4. Births in 2024 were below 2018 in all four quartiles of counties, by 5.6% in the least deprived and 7.3% in the most deprived, and in 2021 the other three quartiles rose by more than the most deprived

Region and deprivation overlap. Of the counties in the most deprived quartile, 45% are in the South, against 24% of the counties in the least deprived quartile. Table 5 splits the quartiles by region. The most deprived quartile lost births in every region: 9.3% (95% CI 6.6% to 11.8%) in the Northeast, 9.2% (95% CI 6.3% to 11.6%) in the Midwest, 5.0% (95% CI 2.9% to 7.0%) in the South and 9.3% in the West. The West's most deprived quartile holds only 5 counties, all of which lost births. A bootstrap over so few counties is mechanical, so no interval is printed for it.

In the South the other three quartiles together changed by +1.1% (95% CI −0.9% to 3.4%), which is higher than the change in the South's most deprived quartile by 6.1 percentage points (95% CI 3.2 percentage points to 9.0 percentage points). The South's flat total therefore combines a loss in its most deprived counties with no clear change elsewhere.

Table 5. The most deprived quartile of counties lost births in every Census region, and in the South the other three quartiles show no clear loss

These are patterns across counties and describe groups of births, not the mothers in any one county. The index measures neighborhoods averaged to counties, and it understates deprivation in high-cost cities, so some counties in the least deprived quartile hold neighborhoods that are more deprived than their rank suggests.

### A larger share of births were to older mothers in 2024

From 2018 to 2024, births fell in every five-year band of mothers aged 15 to 29, by 24.6% (95% CI 22.7% to 26.5%) among mothers aged 15 to 19, by 16.6% (95% CI 15.0% to 18.3%) among mothers aged 20 to 24 and by 11.2% (95% CI 9.6% to 12.9%) among mothers aged 25 to 29. Births to mothers aged 30 to 34 changed by +1.0% (95% CI −0.6% to 2.6%), an interval that includes zero. Births rose by 9.2% (95% CI 7.3% to 11.0%) among mothers aged 35 to 39 and by 19.5% (95% CI 17.0% to 22.3%) among mothers aged 40 to 44 (Table 6).

As shares of births to mothers aged 15 to 44, mothers aged 15 to 24 went from 21.8% (95% CI 21.0% to 22.7%) to 18.7% (95% CI 18.0% to 19.5%), a fall of 3.1 percentage points (95% CI 2.9 percentage points to 3.3 percentage points). Mothers aged 35 to 44 went from 19.7% (95% CI 18.9% to 20.5%) to 22.9% (95% CI 22.1% to 23.8%), a rise of 3.2 percentage points (95% CI 3.1 percentage points to 3.4 percentage points). The shift continues a rise in the mean age of mothers that the National Center for Health Statistics documented for every birth order from 2000 to 2014.[4]

Table 6. Births fell for mothers aged 15 to 29, changed little for mothers aged 30 to 34 and rose for mothers aged 35 to 44 from 2018 to 2024

WONDER splits each county's births by the mother's age in nine bands. Six of them, the bands from 15 to 19 through 40 to 44, are published for nearly every county and year. Of the 24,276 county-year cells for those bands, WONDER withholds 11. Each holds fewer than 10 births, so together they hold at most 99 births, against 20.4 million in published cells.

The other three bands, mothers under 15 and mothers 45 and over, are mostly withheld, with 6,594 of 12,138 cells missing. The published cells hold 0.26% of births and the withheld ones at most 0.29%. The chapter therefore leaves all three bands out and compares mothers aged 15 to 44. A withheld cell is missing, never zero, and nothing is recovered from county totals.

These are births and not birth rates. A fall in births to mothers aged 15 to 19 can mean fewer births per teenager or fewer teenagers in the county, and the files behind this book have no county counts of women by age. A different measure of teen births, for women who grew up in each census tract, is in Chapter 4.2, Teen births (https://vishalsingh.org/zipcode/teen-births).

### The age mix differs more across counties than it changed

In 2018 the share of births to mothers aged 15 to 24 was 17.0% (95% CI 15.6% to 18.3%) in the least deprived quartile of counties and 30.9% (95% CI 29.9% to 32.1%) in the most deprived, a gap of 14.0 percentage points (95% CI 12.3 percentage points to 15.8 percentage points). In 2024 the shares were 14.5% (95% CI 13.4% to 15.5%) and 26.9% (95% CI 25.8% to 28.0%), a gap of 12.4 percentage points (95% CI 11.0 percentage points to 14.0 percentage points).

For mothers aged 35 to 44 the 2018 shares were 24.3% (95% CI 23.1% to 25.5%) in the least deprived quartile and 13.0% (95% CI 12.5% to 13.5%) in the most deprived, a gap of 11.3 percentage points (95% CI 10.0 percentage points to 12.5 percentage points). In 2024 they were 27.8% (95% CI 26.4% to 29.2%) and 15.8% (95% CI 15.1% to 16.5%), a gap of 12.0 percentage points (95% CI 10.5 percentage points to 13.5 percentage points) (Table 7).

Every quartile moved in the same direction. The share of births to mothers aged 15 to 24 fell by 2.5 percentage points (95% CI 1.9 percentage points to 3.0 percentage points) in the least deprived quartile and by 4.0 percentage points (95% CI 3.7 percentage points to 4.4 percentage points) in the most deprived. The share to mothers aged 35 to 44 rose by 3.5 percentage points (95% CI 3.1 percentage points to 3.9 percentage points) and by 2.8 percentage points (95% CI 2.5 percentage points to 3.1 percentage points). The share of young mothers fell by 1.5 percentage points (95% CI 0.9 percentage points to 2.2 percentage points) more in the most deprived quartile. The share of older mothers rose by 0.7 percentage points (95% CI 0.3 percentage points to 1.2 percentage points) more in the least deprived quartile, so the shifts differ in size. Each is much smaller than the gap between quartiles.

Table 7. In every quartile of county deprivation the share of births to older mothers rose and the share to younger mothers fell, and the differences between quartiles are larger than those changes

### Counties that lost the most births lost them among younger mothers

The counties that lost the most births lost them among mothers under 35. Sorting counties by the change in their total births shows where in the age range the loss fell (Table 8). The 144 counties in the quarter with the largest declines, falls of 8.8% or more, lost 13.5% of their births in all. Their births fell by 32.9% among mothers aged 15 to 19, by 25.1% among mothers aged 20 to 24, by 21.1% among mothers aged 25 to 29 and by 8.8% among mothers aged 30 to 34. Births to mothers aged 35 to 39 changed by −0.1%, and births to mothers aged 40 to 44 rose by 9.6%.

The 145 counties in the quarter with the largest gains, gains of 2.6% or more, added 11.2% in all. Births in those counties fell by 13.0% among mothers aged 15 to 19 and by 4.0% among mothers aged 20 to 24, and rose in every older band, from 5.8% among mothers aged 25 to 29 to 39.3% among mothers aged 40 to 44.

Table 8. Counties with the largest declines in births lost births at every age under 35, and counties with the largest gains added births at every age from 25

The groups are formed on the change in total births, so the figure splits each group's change by age and does not test an explanation. A separate question is whether a county's age mix predicts its change. Suppose every age band in a county changed at the all-county rate. The county's 2018 mix would then imply a change in births to mothers aged 15 to 44 between a fall of 8.9% and a fall of 1.3% at the 5th and 95th percentiles of counties. The observed changes run over a much wider range, from a fall of 16.6% to a gain of 19.8%.

The implied and observed changes have a correlation of −0.16 (95% CI −0.26 to −0.06) across 577 counties when counties are weighted by their births and −0.03 (95% CI −0.11 to 0.04) when each counts once. The one county that withholds an age cell is left out. A county's 2018 age mix therefore does not account for which counties lost births. The weighted correlation is small and negative, so counties whose mix implied larger falls lost slightly less.

### What these data cannot show

The chapter reports counts and shares of births and no rates. A birth rate needs the number of women of each age as its denominator, and the files staged for this book hold the total population of counties and tracts but not women by age. A fall in births to mothers aged 20 to 24 can mean fewer births per woman, fewer women in that age group, or both, and so can a gain. County population estimates by age and sex from the Census Bureau would supply the denominator for age-specific rates. Births are counted in the mother's county of residence, so the map is not a map of fertility.

County results describe the 578 counties that WONDER identifies, those with 100,000 or more residents in its population vintage. They hold 79.4% of births in 2024, and they are not a sample of the country. The pooled rows lost fewer births, although those rows include counties that now exceed the line. WONDER's county files used here have no cut by the mother's race or Hispanic origin, so the chapter cannot say whether the shift in mothers' ages differs by group.

The deprivation comparison is descriptive. The Area Deprivation Index describes neighborhoods in 2019 to 2023 and is averaged to counties, and region and deprivation overlap. The comparison of quartiles says nothing about why births fell in any county. It is an ecological pattern, and it need not hold for the people inside the counties. The comparison of 2018 with 2024 uses the endpoint years only. A county with few births moves from year to year by chance, so a county's direction of change is better established than its rank among the named counties.

## Tables

### Table 1. Births in the named counties fell 4.6% from 2018 to 2024 with a low in 2023, a larger fall than the 3.0% in all other counties

Live births by year in the 578 counties that CDC WONDER identifies (counties with 100,000 or more residents in WONDER's population vintage) and in all other counties, which WONDER pools by state, 2018 to 2024, indexed to 2018 or as counts

| measure | n | series | value | year |
| --- | ---: | --- | ---: | ---: |
| index | 3,020,813 | Named counties | 100 | 2018 |
| births | 3,020,813 | Named counties | 3020813 | 2018 |
| index | 2,985,056 | Named counties | 98.82 | 2019 |
| births | 2,985,056 | Named counties | 2985056 | 2019 |
| index | 2,875,172 | Named counties | 95.18 | 2020 |
| births | 2,875,172 | Named counties | 2875172 | 2020 |
| index | 2,912,953 | Named counties | 96.43 | 2021 |
| births | 2,912,953 | Named counties | 2912953 | 2021 |
| index | 2,920,239 | Named counties | 96.67 | 2022 |
| births | 2,920,239 | Named counties | 2920239 | 2022 |
| index | 2,855,036 | Named counties | 94.51 | 2023 |
| births | 2,855,036 | Named counties | 2855036 | 2023 |
| index | 2,881,385 | Named counties | 95.38 | 2024 |
| births | 2,881,385 | Named counties | 2881385 | 2024 |
| index | 770,899 | Other counties | 100 | 2018 |
| births | 770,899 | Other counties | 770899 | 2018 |
| index | 762,484 | Other counties | 98.91 | 2019 |
| births | 762,484 | Other counties | 762484 | 2019 |
| index | 738,475 | Other counties | 95.79 | 2020 |
| births | 738,475 | Other counties | 738475 | 2020 |
| index | 751,339 | Other counties | 97.46 | 2021 |
| births | 751,339 | Other counties | 751339 | 2021 |
| index | 747,519 | Other counties | 96.97 | 2022 |
| births | 747,519 | Other counties | 747519 | 2022 |
| index | 740,981 | Other counties | 96.12 | 2023 |
| births | 740,981 | Other counties | 740981 | 2023 |
| index | 747,549 | Other counties | 96.97 | 2024 |
| births | 747,549 | Other counties | 747549 | 2024 |

Views: Index, 2018 = 100 (measure = index); Live births (measure = births).

Note: The named counties are the 578 that CDC WONDER natality identifies in every year from 2018 to 2024: counties with 100,000 or more residents in the population vintage WONDER uses, which is earlier than the 2020 Census. WONDER pools the births of every other county in a state into one row, so those counties are not in the named counties.

Note: Births are full counts from birth certificates, so no interval is drawn. A count of births is not a birth rate: the series blends births per woman with the number of women.

Source: CDC WONDER natality, births in 2018-2024; full counts of births (no sampling error)

Data: https://vishalsingh.org/zipcode/report/where-births-are-falling/figures/births_trend.json

### Table 2. Of the 58 counties with the largest gains in births, 43 are in the South, which holds 40.1% of the named counties

Percent change in live births from 2018 to 2024 by county, for the 578 counties that CDC WONDER identifies (counties with 100,000 or more residents in WONDER's population vintage)

No inline rows: the values of Table 2 are in https://vishalsingh.org/zipcode/data/where-births-are-falling/births_change_map.json.

Note: The named counties are the 578 that CDC WONDER natality identifies in every year from 2018 to 2024: counties with 100,000 or more residents in the population vintage WONDER uses, which is earlier than the 2020 Census. WONDER pools the births of every other county in a state into one row, so those counties are not in the named counties.

Note: Births are full counts, so no interval is drawn for a county. A small county's count moves more from year to year by chance, so the shading of a county with few births is less stable than the shading of a large one.

Note: The tooltip gives the value of a county whose change is beyond the end of the key.

Note: Connecticut is shown as its eight legacy counties, the coding of the source. Alaska is drawn. Puerto Rico is not in these data and is not drawn.

Source: CDC WONDER natality, births in 2018-2024; full counts of births (no sampling error); county changes are not weighted

Data: https://vishalsingh.org/zipcode/report/where-births-are-falling/figures/births_change_map.json

### Table 3. The ten largest gains in births are all in the South, and the ten largest declines are spread across every Census region

Percent change in live births from 2018 to 2024 for the ten named counties with the largest gains and the ten with the largest declines, of the 578 named counties

| births_2018 | births_2024 | change | county | group |
| ---: | ---: | ---: | --- | --- |
| 1786 | 2993 | 67.58 | Kaufman County, TX | Largest gains |
| 1526 | 2203 | 44.36 | Comal County, TX | Largest gains |
| 2572 | 3670 | 42.69 | Hays County, TX | Largest gains |
| 6650 | 9325 | 40.23 | Williamson County, TX | Largest gains |
| 1537 | 2096 | 36.37 | Parker County, TX | Largest gains |
| 987 | 1320 | 33.74 | Brunswick County, NC | Largest gains |
| 2214 | 2914 | 31.62 | Ellis County, TX | Largest gains |
| 2299 | 2975 | 29.40 | Johnston County, NC | Largest gains |
| 1173 | 1501 | 27.96 | Bartow County, GA | Largest gains |
| 7355 | 9220 | 25.36 | Montgomery County, TX | Largest gains |
| 4127 | 3142 | −23.87 | St. Louis city, MO | Largest declines |
| 3041 | 2361 | −22.36 | Hinds County, MS | Largest declines |
| 1364 | 1062 | −22.14 | Humboldt County, CA | Largest declines |
| 3109 | 2449 | −21.23 | St. Clair County, IL | Largest declines |
| 1518 | 1204 | −20.69 | Monroe County, PA | Largest declines |
| 1506 | 1195 | −20.65 | Terrebonne Parish, LA | Largest declines |
| 8697 | 6930 | −20.32 | San Francisco County, CA | Largest declines |
| 1326 | 1072 | −19.16 | Fayette County, PA | Largest declines |
| 4656 | 3769 | −19.05 | Orleans Parish, LA | Largest declines |
| 1246 | 1010 | −18.94 | Monroe County, IN | Largest declines |

Note: The named counties are the 578 that CDC WONDER natality identifies in every year from 2018 to 2024: counties with 100,000 or more residents in the population vintage WONDER uses, which is earlier than the 2020 Census. WONDER pools the births of every other county in a state into one row, so those counties are not in the named counties.

Note: Births are full counts, so no interval is drawn. The data table lists each county's births in 2018 and 2024.

Source: CDC WONDER natality, births in 2018-2024; full counts of births (no sampling error); county changes are not weighted

Data: https://vishalsingh.org/zipcode/report/where-births-are-falling/figures/births_change_extremes.json

### Table 4. Births in 2024 were below 2018 in all four quartiles of counties, by 5.6% in the least deprived and 7.3% in the most deprived, and in 2021 the other three quartiles rose by more than the most deprived

Pooled live births in each quartile of the 578 named counties by Area Deprivation Index rank, indexed to 2018 = 100, 2018 to 2024, with 95% intervals from a bootstrap over counties

| conf_high | conf_low | index | n | quartile | year |
| ---: | ---: | ---: | ---: | --- | ---: |
| n/a | n/a | 100 | 1,224,834 | Least deprived quartile | 2018 |
| 99 | 98.12 | 98.51 | 1,206,641 | Least deprived quartile | 2019 |
| 95.57 | 93.10 | 94.28 | 1,154,721 | Least deprived quartile | 2020 |
| 97.84 | 93.85 | 95.77 | 1,173,023 | Least deprived quartile | 2021 |
| 97.77 | 93.60 | 95.59 | 1,170,851 | Least deprived quartile | 2022 |
| 95.57 | 90.73 | 93.09 | 1,140,185 | Least deprived quartile | 2023 |
| 97.19 | 91.77 | 94.43 | 1,156,626 | Least deprived quartile | 2024 |
| n/a | n/a | 100 | 710,664 | Second quartile | 2018 |
| 99.18 | 97.97 | 98.56 | 700,447 | Second quartile | 2019 |
| 96.58 | 94.40 | 95.43 | 678,194 | Second quartile | 2020 |
| 99.46 | 95.68 | 97.54 | 693,209 | Second quartile | 2021 |
| 100.9 | 95.90 | 98.47 | 699,762 | Second quartile | 2022 |
| 99.12 | 93.81 | 96.40 | 685,072 | Second quartile | 2023 |
| 100.6 | 94.70 | 97.44 | 692,445 | Second quartile | 2024 |
| n/a | n/a | 100 | 630,186 | Third quartile | 2018 |
| 99.75 | 98.96 | 99.31 | 625,862 | Third quartile | 2019 |
| 96.79 | 95.72 | 96.20 | 606,252 | Third quartile | 2020 |
| 98.35 | 96.20 | 97.14 | 612,146 | Third quartile | 2021 |
| 98.90 | 96.93 | 97.88 | 616,853 | Third quartile | 2022 |
| 97.59 | 95.05 | 96.34 | 607,127 | Third quartile | 2023 |
| 98.42 | 95.52 | 96.86 | 610,399 | Third quartile | 2024 |
| n/a | n/a | 100 | 455,129 | Most deprived quartile | 2018 |
| 99.76 | 98.90 | 99.34 | 452,106 | Most deprived quartile | 2019 |
| 96.26 | 95.35 | 95.80 | 436,005 | Most deprived quartile | 2020 |
| 96.17 | 94.80 | 95.48 | 434,575 | Most deprived quartile | 2021 |
| 96.14 | 93.99 | 95.09 | 432,773 | Most deprived quartile | 2022 |
| 94.09 | 91.59 | 92.86 | 422,652 | Most deprived quartile | 2023 |
| 94.20 | 91.23 | 92.70 | 421,915 | Most deprived quartile | 2024 |

Note: The named counties are the 578 that CDC WONDER natality identifies in every year from 2018 to 2024: counties with 100,000 or more residents in the population vintage WONDER uses, which is earlier than the 2020 Census. WONDER pools the births of every other county in a state into one row, so those counties are not in the named counties.

Note: A tract's Area Deprivation Index national rank (1 is least deprived, 100 most) is the unweighted mean of the ranks of its block groups. A county's deprivation rank is the mean of its tracts' ranks weighted by 2019-2023 tract population. Quartiles hold equal numbers of the named counties, so the most deprived quartile is relative to large counties and not to the nation. The index is a measure of neighborhoods, averaged to counties.

Note: Intervals are 95% intervals from a bootstrap over counties (replicates and seed in the methods note). Births are full counts, so an interval shows how much a pooled figure depends on which counties are in the group, not sampling error in the counts. The 2018 point is the base and has no interval.

Source: CDC WONDER natality, births in 2018-2024; full counts of births; counties grouped by Area Deprivation Index 2023 with ACS 2019-2023 tract population (population-weighted); pooled over counties by births (births-weighted); intervals from a bootstrap over counties

Data: https://vishalsingh.org/zipcode/report/where-births-are-falling/figures/births_by_deprivation.json

### Table 5. The most deprived quartile of counties lost births in every Census region, and in the South the other three quartiles show no clear loss

Pooled change in live births from 2018 to 2024 by Census region and quartile of county deprivation rank, named counties, with 95% intervals from a bootstrap over counties

| births_2018 | change | conf_high | conf_low | n_lost_births | n_units | quartile | region |
| ---: | ---: | ---: | ---: | ---: | ---: | --- | --- |
| 338526 | −4.36 | 0.120 | −7.66 | 24 | 39 | Least deprived quartile | Northeast |
| 76401 | −1.99 | −0.060 | −3.67 | 16 | 25 | Second quartile | Northeast |
| 96145 | −7.73 | −4.41 | −9.89 | 20 | 24 | Third quartile | Northeast |
| 48096 | −9.26 | −6.59 | −11.84 | 21 | 22 | Most deprived quartile | Northeast |
| 52620 | −5.68 | n/a | n/a | 6 | 9 | Least deprived quartile | Midwest |
| 158400 | −10.63 | −4.34 | −14.08 | 19 | 26 | Second quartile | Midwest |
| 156974 | −6.13 | −4.79 | −7.50 | 46 | 49 | Third quartile | Midwest |
| 189123 | −9.20 | −6.26 | −11.60 | 44 | 53 | Most deprived quartile | Midwest |
| 183903 | 2.15 | 8.71 | −4.06 | 17 | 35 | Least deprived quartile | South |
| 371925 | 1.30 | 4.59 | −1.59 | 25 | 69 | Second quartile | South |
| 335404 | 0.340 | 3.71 | −1.79 | 23 | 63 | Third quartile | South |
| 208110 | −5.02 | −2.92 | −6.95 | 43 | 65 | Most deprived quartile | South |
| 649785 | −8.37 | −4.74 | −11.55 | 46 | 61 | Least deprived quartile | West |
| 103938 | −4.51 | 1.79 | −7.96 | 17 | 25 | Second quartile | West |
| 41663 | −9.28 | n/a | n/a | 8 | 8 | Third quartile | West |
| 9800 | −9.27 | n/a | n/a | 5 | 5 | Most deprived quartile | West |

Note: The named counties are the 578 that CDC WONDER natality identifies in every year from 2018 to 2024: counties with 100,000 or more residents in the population vintage WONDER uses, which is earlier than the 2020 Census. WONDER pools the births of every other county in a state into one row, so those counties are not in the named counties.

Note: A tract's Area Deprivation Index national rank (1 is least deprived, 100 most) is the unweighted mean of the ranks of its block groups. A county's deprivation rank is the mean of its tracts' ranks weighted by 2019-2023 tract population. Quartiles hold equal numbers of the named counties, so the most deprived quartile is relative to large counties and not to the nation. The index is a measure of neighborhoods, averaged to counties.

Note: Intervals are 95% intervals from a bootstrap over counties (replicates and seed in the methods note). Births are full counts, so an interval shows how much a pooled figure depends on which counties are in the group, not sampling error in the counts. A cell with fewer than 10 counties shows no interval; in the West, the most deprived and third quartiles hold few counties, and the least deprived quartile of the Midwest holds fewer than 10, so those cells are thin.

Note: The Census South region is 16 states and DC; the Northeast, Midwest and West follow the Census Bureau's regions.

Source: CDC WONDER natality, births in 2018-2024; full counts of births; counties grouped by Area Deprivation Index 2023 with ACS 2019-2023 tract population (population-weighted); pooled over counties by births (births-weighted); intervals from a bootstrap over counties

Data: https://vishalsingh.org/zipcode/report/where-births-are-falling/figures/births_change_region_quartile.json

### Table 6. Births fell for mothers aged 15 to 29, changed little for mothers aged 30 to 34 and rose for mothers aged 35 to 44 from 2018 to 2024

Pooled change in live births by mother's age band, 2018 to 2024, in the 578 named counties, with 95% intervals from a bootstrap over counties

| age | births_2018 | births_2024 | change | conf_high | conf_low | n_units |
| --- | ---: | ---: | ---: | ---: | ---: | ---: |
| 15 to 19 | 129757 | 97772 | −24.65 | −22.72 | −26.53 | 577 |
| 20 to 24 | 527582 | 439765 | −16.65 | −14.98 | −18.31 | 578 |
| 25 to 29 | 848726 | 753795 | −11.19 | −9.57 | −12.87 | 578 |
| 30 to 34 | 910977 | 920282 | 1.02 | 2.65 | −0.620 | 578 |
| 35 to 39 | 490705 | 535630 | 9.16 | 11.05 | 7.32 | 578 |
| 40 to 44 | 103030 | 123085 | 19.47 | 22.34 | 17.02 | 578 |

Note: The named counties are the 578 that CDC WONDER natality identifies in every year from 2018 to 2024: counties with 100,000 or more residents in the population vintage WONDER uses, which is earlier than the 2020 Census. WONDER pools the births of every other county in a state into one row, so those counties are not in the named counties.

Note: Intervals are 95% intervals from a bootstrap over counties (replicates and seed in the methods note). Births are full counts, so an interval shows how much a pooled figure depends on which counties are in the group, not sampling error in the counts.

Note: WONDER splits births into nine age bands. Mothers under 15 and mothers 45 and over are left out because WONDER withholds most of those cells; the methods note gives the counts. A withheld cell is missing, never zero, and a county that withholds a band in 2018 or 2024 is left out of that band's bar; the data table gives the number of counties in each bar.

Source: CDC WONDER natality, births in 2018-2024; full counts of births by mother's age; changes pooled over counties; intervals from a bootstrap over counties

Data: https://vishalsingh.org/zipcode/report/where-births-are-falling/figures/births_by_mother_age.json

### Table 7. In every quartile of county deprivation the share of births to older mothers rose and the share to younger mothers fell, and the differences between quartiles are larger than those changes

Share of births to mothers aged 15 to 24 and to mothers aged 35 to 44, among births to mothers aged 15 to 44, by quartile of county deprivation rank, 2018 and 2024, with 95% intervals from a bootstrap over counties

| group_label | hi1 | hi2 | lo1 | lo2 | measure | n_units | y2018 | y2024 |
| --- | ---: | ---: | ---: | ---: | --- | ---: | ---: | ---: |
| All named counties | 22.67 | 19.48 | 20.99 | 17.98 | Mothers aged 15 to 24 | 578 | 21.83 | 18.73 |
| Least deprived quartile | 18.27 | 15.51 | 15.57 | 13.42 | Mothers aged 15 to 24 | 144 | 16.96 | 14.46 |
| Second quartile | 22.09 | 18.75 | 20.07 | 16.95 | Mothers aged 15 to 24 | 145 | 21.01 | 17.80 |
| Third quartile | 26.55 | 23.11 | 24.72 | 21.20 | Mothers aged 15 to 24 | 144 | 25.63 | 22.18 |
| Most deprived quartile | 32.08 | 28.03 | 29.93 | 25.83 | Mothers aged 15 to 24 | 145 | 30.94 | 26.91 |
| All named counties | 20.51 | 23.80 | 18.92 | 22.08 | Mothers aged 35 to 44 | 578 | 19.72 | 22.95 |
| Least deprived quartile | 25.46 | 29.18 | 23.05 | 26.40 | Mothers aged 35 to 44 | 144 | 24.32 | 27.84 |
| Second quartile | 20.45 | 23.86 | 18.51 | 21.75 | Mothers aged 35 to 44 | 145 | 19.53 | 22.86 |
| Third quartile | 16.41 | 19.40 | 15.17 | 18.01 | Mothers aged 35 to 44 | 144 | 15.87 | 18.76 |
| Most deprived quartile | 13.50 | 16.52 | 12.50 | 15.07 | Mothers aged 35 to 44 | 145 | 13.01 | 15.79 |

Note: The named counties are the 578 that CDC WONDER natality identifies in every year from 2018 to 2024: counties with 100,000 or more residents in the population vintage WONDER uses, which is earlier than the 2020 Census. WONDER pools the births of every other county in a state into one row, so those counties are not in the named counties.

Note: A tract's Area Deprivation Index national rank (1 is least deprived, 100 most) is the unweighted mean of the ranks of its block groups. A county's deprivation rank is the mean of its tracts' ranks weighted by 2019-2023 tract population. Quartiles hold equal numbers of the named counties, so the most deprived quartile is relative to large counties and not to the nation. The index is a measure of neighborhoods, averaged to counties.

Note: Intervals are 95% intervals from a bootstrap over counties (replicates and seed in the methods note). Births are full counts, so an interval shows how much a pooled figure depends on which counties are in the group, not sampling error in the counts. Shares are of births to mothers aged 15 to 44; mothers under 15 and mothers 45 and over are left out, and withheld cells are missing.

Source: CDC WONDER natality, births in 2018-2024; full counts of births by mother's age; counties grouped by Area Deprivation Index 2023 with ACS 2019-2023 tract population (population-weighted); pooled over counties by births (births-weighted); intervals from a bootstrap over counties

Data: https://vishalsingh.org/zipcode/report/where-births-are-falling/figures/mother_age_by_deprivation.json

### Table 8. Counties with the largest declines in births lost births at every age under 35, and counties with the largest gains added births at every age from 25

Pooled change in live births from 2018 to 2024 by mother's age band, in four equal-sized groups of the 578 named counties formed by the change in their total births

| age | age_position | change | group | n_units |
| --- | ---: | ---: | --- | ---: |
| 15 to 19 | 1 | −32.87 | Largest declines | 144 |
| 20 to 24 | 2 | −25.09 | Largest declines | 144 |
| 25 to 29 | 3 | −21.11 | Largest declines | 144 |
| 30 to 34 | 4 | −8.77 | Largest declines | 144 |
| 35 to 39 | 5 | −0.060 | Largest declines | 144 |
| 40 to 44 | 6 | 9.55 | Largest declines | 144 |
| 15 to 19 | 1 | −25.21 | Smaller declines | 145 |
| 20 to 24 | 2 | −17.85 | Smaller declines | 145 |
| 25 to 29 | 3 | −13.39 | Smaller declines | 145 |
| 30 to 34 | 4 | −0.670 | Smaller declines | 145 |
| 35 to 39 | 5 | 9.07 | Smaller declines | 145 |
| 40 to 44 | 6 | 20.34 | Smaller declines | 145 |
| 15 to 19 | 1 | −20.90 | Little change | 144 |
| 20 to 24 | 2 | −12.76 | Little change | 144 |
| 25 to 29 | 3 | −7.43 | Little change | 144 |
| 30 to 34 | 4 | 4.50 | Little change | 144 |
| 35 to 39 | 5 | 13.88 | Little change | 144 |
| 40 to 44 | 6 | 23.02 | Little change | 144 |
| 15 to 19 | 1 | −12.97 | Largest gains | 144 |
| 20 to 24 | 2 | −4.05 | Largest gains | 145 |
| 25 to 29 | 3 | 5.80 | Largest gains | 145 |
| 30 to 34 | 4 | 19.11 | Largest gains | 145 |
| 35 to 39 | 5 | 24.75 | Largest gains | 145 |
| 40 to 44 | 6 | 39.26 | Largest gains | 145 |

Note: The named counties are the 578 that CDC WONDER natality identifies in every year from 2018 to 2024: counties with 100,000 or more residents in the population vintage WONDER uses, which is earlier than the 2020 Census. WONDER pools the births of every other county in a state into one row, so those counties are not in the named counties.

Note: Counties are sorted into four groups of equal size by their percent change in total births from 2018 to 2024: the largest-decline group has falls of 8.8% or more, and the largest-gain group has gains of 2.6% or more. Births are full counts, so no interval is drawn; the groups are formed on the outcome, so an interval would not describe a draw of counties.

Note: A county that withholds a band in 2018 or 2024 is left out of that band's point.

Source: CDC WONDER natality, births in 2018-2024; full counts of births by mother's age; changes pooled over counties in each group

Data: https://vishalsingh.org/zipcode/report/where-births-are-falling/figures/age_change_by_county_change.json

## All estimates

Every fact in facts.json (155), sorted by id.

| Fact id | Value | Unit | Estimand | Population | Period | Interval | n | Weights | Source | Note |
| --- | ---: | --- | --- | --- | --- | --- | ---: | --- | --- | --- |
| age_15 | 15 | years of age | age below which WONDER's under-15 band applies; mothers under this age are left out (a definition) | mothers | all years (a definition) |   |   | none (definition) | CDC WONDER natality |   |
| age_25 | 25 | years of age | age from which births rise in the largest-gain counties (a definition of the band boundary used in the figure title) | mothers | all years (a definition) |   |   | none (definition) | CDC WONDER natality |   |
| age_35 | 35 | years of age | age below which a mother belongs to the younger groups in this chapter (a definition) | mothers | all years (a definition) |   |   | none (definition) | CDC WONDER natality |   |
| age_45 | 45 | years of age | age at which WONDER's 45-to-49 band begins; mothers of this age and older are left out (a definition) | mothers | all years (a definition) |   |   | none (definition) | CDC WONDER natality |   |
| band_1519 | 15 to 19 | years of age | age-of-mother range used in this chapter, from WONDER's five-year bands (a definition) | mothers | all years (a definition) |   |   | none (definition) | CDC WONDER natality |   |
| band_1524 | 15 to 24 | years of age | age-of-mother range used in this chapter, from WONDER's five-year bands (a definition) | mothers | all years (a definition) |   |   | none (definition) | CDC WONDER natality |   |
| band_1529 | 15 to 29 | years of age | age-of-mother range used in this chapter, from WONDER's five-year bands (a definition) | mothers | all years (a definition) |   |   | none (definition) | CDC WONDER natality |   |
| band_1544 | 15 to 44 | years of age | age-of-mother range used in this chapter, from WONDER's five-year bands (a definition) | mothers | all years (a definition) |   |   | none (definition) | CDC WONDER natality |   |
| band_2024 | 20 to 24 | years of age | age-of-mother range used in this chapter, from WONDER's five-year bands (a definition) | mothers | all years (a definition) |   |   | none (definition) | CDC WONDER natality |   |
| band_2529 | 25 to 29 | years of age | age-of-mother range used in this chapter, from WONDER's five-year bands (a definition) | mothers | all years (a definition) |   |   | none (definition) | CDC WONDER natality |   |
| band_3034 | 30 to 34 | years of age | age-of-mother range used in this chapter, from WONDER's five-year bands (a definition) | mothers | all years (a definition) |   |   | none (definition) | CDC WONDER natality |   |
| band_3539 | 35 to 39 | years of age | age-of-mother range used in this chapter, from WONDER's five-year bands (a definition) | mothers | all years (a definition) |   |   | none (definition) | CDC WONDER natality |   |
| band_3544 | 35 to 44 | years of age | age-of-mother range used in this chapter, from WONDER's five-year bands (a definition) | mothers | all years (a definition) |   |   | none (definition) | CDC WONDER natality |   |
| band_4044 | 40 to 44 | years of age | age-of-mother range used in this chapter, from WONDER's five-year bands (a definition) | mothers | all years (a definition) |   |   | none (definition) | CDC WONDER natality |   |
| births_named_2018 | 3.02 million | live births | count of live births | live births in the counties that CDC WONDER natality identifies in every year (counties with 100,000 or more residents in the population vintage WONDER uses) | 2018 |   |   | none (full count) | CDC WONDER natality |   |
| births_named_2024 | 2.88 million | live births | count of live births | live births in the counties that CDC WONDER natality identifies in every year (counties with 100,000 or more residents in the population vintage WONDER uses) | 2024 |   |   | none (full count) | CDC WONDER natality |   |
| births_pooled_2018 | 0.77 million | live births | count of live births in the pooled rows | live births in the counties that WONDER natality does not name, which it pools within each state | 2018 |   |   | none (full count) | CDC WONDER natality |   |
| births_pooled_2024 | 0.75 million | live births | count of live births in the pooled rows | live births in the counties that WONDER natality does not name, which it pools within each state | 2024 |   |   | none (full count) | CDC WONDER natality |   |
| births_published_cells | 20.4 million | live births | count of births in published cells | live births in the published age-of-mother cells of the named counties | births in 2018 to 2024 |   | 20,431,379 births | none (full count) | CDC WONDER natality |   |
| bottom_tenth_cut | 13.6% | percent of 2018 births | fall at the 10th percentile of the county changes in births | named counties | births in 2018 and 2024 |   | 578 counties | none (full count) | CDC WONDER natality |   |
| bottom_tenth_n | 58 | counties | count of counties at or below the 10th percentile of change | named counties in the bottom tenth of change in births | births in 2018 and 2024 |   |   | none (full count) | CDC WONDER natality |   |
| bottom_tenth_south | 13 | counties | count of those counties in the Census South region (16 states and DC) | named counties in the bottom tenth of change that are in the Census South region | births in 2018 and 2024 |   |   | none (full count) | CDC WONDER natality |   |
| change_2021_q4 | −0.3% | percent of 2020 births | pooled change in the count of births from 2020 to 2021, bootstrap interval over counties | live births in the most deprived quartile of the named counties by county Area Deprivation Index rank | 2020 to 2021 | 95% CI −0.8% to 0.1% | 145 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| chg_3034 | +1.0% | percent of 2018 births | pooled change in the count of births from 2018 to 2024, bootstrap interval over counties | live births to mothers aged 30 to 34 in the named counties that publish the band in both years | births in 2018 and 2024 | 95% CI −0.6% to 2.6% | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| core_cells | 24,276 | cells | count of cells | county-year-by-age cells for mothers aged 15 to 44 in the named counties | births in 2018 to 2024 |   |   | none (full count) | CDC WONDER natality |   |
| core_withheld_cells | 11 | cells | count of cells with 1 to 9 births, which WONDER withholds | county-year-by-age cells for mothers aged 15 to 44 in the named counties | births in 2018 to 2024 |   |   | none (full count) | CDC WONDER natality |   |
| core_withheld_max_births | 99 | live births | largest number of births the withheld cells could hold: 9 births in each | withheld cells for mothers aged 15 to 44 | births in 2018 to 2024 |   |   | none (full count) | CDC WONDER natality |   |
| counties_declined | 380 | counties | count of counties with fewer births in 2024 than in 2018 | named counties | births in 2018 and 2024 |   |   | none (full count) | CDC WONDER natality |   |
| counties_rose | 197 | counties | count of counties with more births in 2024 than in 2018 | named counties | births in 2018 and 2024 |   |   | none (full count) | CDC WONDER natality |   |
| counties_unchanged | one | counties | count of counties with the same number of births in 2018 and 2024 | named counties | births in 2018 and 2024 |   |   | none (full count) | CDC WONDER natality |   |
| counties_used | 578 | counties | count of counties | counties that WONDER natality identifies in every year from 2018 to 2024 and that have births | births in 2018 to 2024 |   |   | none (full count) | CDC WONDER natality |   |
| county_median_decline | 3.8% | percent of 2018 births | median of the county changes in births, one county one count | the median named county | births in 2018 and 2024 |   | 578 counties | none (full count) | CDC WONDER natality |   |
| county_p5_decline | 16.5% | percent of 2018 births | 5th percentile of the county changes in births | named counties at the 5th percentile of change | births in 2018 and 2024 |   | 578 counties | none (full count) | CDC WONDER natality |   |
| county_p95_gain | 19.9% | percent of 2018 births | 95th percentile of the county changes in births | named counties at the 95th percentile of change | births in 2018 and 2024 |   | 578 counties | none (full count) | CDC WONDER natality |   |
| decline_2020 | 4.8% | percent of 2018 births | fall in the count of births from 2018 to 2020 | live births in the counties that CDC WONDER natality identifies in every year (counties with 100,000 or more residents in the population vintage WONDER uses) | 2018 to 2020 |   |   | none (full count) | CDC WONDER natality |   |
| decline_2023 | 5.5% | percent of 2018 births | fall in the count of births from 2018 to 2023 | live births in the counties that CDC WONDER natality identifies in every year (counties with 100,000 or more residents in the population vintage WONDER uses) | 2018 to 2023 |   |   | none (full count) | CDC WONDER natality |   |
| decline_mid | 2.8% | percent of 2018 births | fall in the pooled count of births from 2018 to 2024, bootstrap interval over counties | live births in the second and third quartiles together of the named counties by county Area Deprivation Index rank | births in 2018 and 2024 | 95% CI 1.1% to 4.5% | 289 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| decline_named | 4.6% | percent of 2018 births | fall in the count of births from 2018 to 2024 | live births in the counties that CDC WONDER natality identifies in every year (counties with 100,000 or more residents in the population vintage WONDER uses) | 2018 to 2024 |   |   | none (full count) | CDC WONDER natality |   |
| decline_pooled | 3.0% | percent of 2018 births | fall in the count of births in the pooled rows from 2018 to 2024 | live births in the counties that WONDER natality does not name, which it pools within each state | 2018 to 2024 |   |   | none (full count) | CDC WONDER natality |   |
| decline_q1 | 5.6% | percent of 2018 births | fall in the pooled count of births from 2018 to 2024, bootstrap interval over counties | live births in the least deprived quartile of the named counties by county Area Deprivation Index rank | births in 2018 and 2024 | 95% CI 2.8% to 8.2% | 144 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| decline_q2 | 2.6% | percent of 2018 births | fall in the pooled count of births from 2018 to 2024, bootstrap interval over counties | live births in the second quartile of the named counties by county Area Deprivation Index rank | births in 2018 and 2024 | 95% CI −0.6% to 5.3% | 145 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| decline_q3 | 3.1% | percent of 2018 births | fall in the pooled count of births from 2018 to 2024, bootstrap interval over counties | live births in the third quartile of the named counties by county Area Deprivation Index rank | births in 2018 and 2024 | 95% CI 1.6% to 4.5% | 144 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| decline_q4 | 7.3% | percent of 2018 births | fall in the pooled count of births from 2018 to 2024, bootstrap interval over counties | live births in the most deprived quartile of the named counties by county Area Deprivation Index rank | births in 2018 and 2024 | 95% CI 5.8% to 8.8% | 145 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| decline_us | 4.3% | percent of 2018 births | fall in the count of births from 2018 to 2024 | live births in the 50 states and DC | 2018 to 2024 |   |   | none (full count) | CDC WONDER natality |   |
| empty_shells | two | counties | count of listed counties whose births WONDER folded into the state's pooled row | county identifiers that WONDER lists in every year from 2018 to 2024 but with no births (Cape May County NJ, Portsmouth city VA) | births in 2018 to 2024 |   |   | none (full count) | CDC WONDER natality |   |
| ext_min_births | 987 | live births | smallest 2018 count of births among those counties | the 20 counties in the figure of largest gains and declines | 2018 |   | 20 counties | none (full count) | CDC WONDER natality |   |
| ext_n | ten | counties | number of counties listed in each group of largest gains and largest declines (a definition) | named counties | all years (a definition) |   |   | none (definition) | CDC WONDER natality |   |
| fall_1519 | 24.6% | percent of 2018 births | pooled change in the count of births from 2018 to 2024, bootstrap interval over counties | live births to mothers aged 15 to 19 in the named counties that publish the band in both years | births in 2018 and 2024 | 95% CI 22.7% to 26.5% | 577 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| fall_2024 | 16.6% | percent of 2018 births | pooled change in the count of births from 2018 to 2024, bootstrap interval over counties | live births to mothers aged 20 to 24 in the named counties that publish the band in both years | births in 2018 and 2024 | 95% CI 15.0% to 18.3% | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| fall_2529 | 11.2% | percent of 2018 births | pooled change in the count of births from 2018 to 2024, bootstrap interval over counties | live births to mothers aged 25 to 29 in the named counties that publish the band in both years | births in 2018 and 2024 | 95% CI 9.6% to 12.9% | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| fall_share_young | 3.1 percentage points | percentage points | change from 2018 to 2024 in the pooled share of births, shared bootstrap draws over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually, births in published cells; mothers aged 15 to 24 | births in 2018 and 2024 | 95% CI 2.9 percentage points to 3.3 percentage points | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| fall_young_diff | 1.5 percentage points | percentage points | difference of two changes in pooled shares: fall in the share of births to mothers aged 15 to 24, most deprived quartile minus least deprived quartile, shared bootstrap draws over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually | births in 2018 and 2024 | 95% CI 0.9 percentage points to 2.2 percentage points | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| fall_young_q1 | 2.5 percentage points | percentage points | change from 2018 to 2024 in the pooled share of births, shared bootstrap draws over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually; mothers aged 15 to 24; least deprived quartile | births in 2018 and 2024 | 95% CI 1.9 percentage points to 3.0 percentage points | 144 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| fall_young_q4 | 4.0 percentage points | percentage points | change from 2018 to 2024 in the pooled share of births, shared bootstrap draws over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually; mothers aged 15 to 24; most deprived quartile | births in 2018 and 2024 | 95% CI 3.7 percentage points to 4.4 percentage points | 145 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| g1_chg_3539 | −0.1% | percent of 2018 births | pooled change in the count of births from 2018 to 2024 | live births to mothers aged 35 to 39 in the quarter of named counties with the largest declines that publish the band in both years | births in 2018 and 2024 |   | 144 counties | births (a pooled ratio of totals over counties; full counts) | CDC WONDER natality |   |
| g1_fall_1519 | 32.9% | percent of 2018 births | pooled change in the count of births from 2018 to 2024 | live births to mothers aged 15 to 19 in the quarter of named counties with the largest declines that publish the band in both years | births in 2018 and 2024 |   | 144 counties | births (a pooled ratio of totals over counties; full counts) | CDC WONDER natality |   |
| g1_fall_2024 | 25.1% | percent of 2018 births | pooled change in the count of births from 2018 to 2024 | live births to mothers aged 20 to 24 in the quarter of named counties with the largest declines that publish the band in both years | births in 2018 and 2024 |   | 144 counties | births (a pooled ratio of totals over counties; full counts) | CDC WONDER natality |   |
| g1_fall_2529 | 21.1% | percent of 2018 births | pooled change in the count of births from 2018 to 2024 | live births to mothers aged 25 to 29 in the quarter of named counties with the largest declines that publish the band in both years | births in 2018 and 2024 |   | 144 counties | births (a pooled ratio of totals over counties; full counts) | CDC WONDER natality |   |
| g1_fall_3034 | 8.8% | percent of 2018 births | pooled change in the count of births from 2018 to 2024 | live births to mothers aged 30 to 34 in the quarter of named counties with the largest declines that publish the band in both years | births in 2018 and 2024 |   | 144 counties | births (a pooled ratio of totals over counties; full counts) | CDC WONDER natality |   |
| g1_rise_4044 | 9.6% | percent of 2018 births | pooled change in the count of births from 2018 to 2024 | live births to mothers aged 40 to 44 in the quarter of named counties with the largest declines that publish the band in both years | births in 2018 and 2024 |   | 144 counties | births (a pooled ratio of totals over counties; full counts) | CDC WONDER natality |   |
| g4_fall_1519 | 13.0% | percent of 2018 births | pooled change in the count of births from 2018 to 2024 | live births to mothers aged 15 to 19 in the quarter of named counties with the largest gains that publish the band in both years | births in 2018 and 2024 |   | 144 counties | births (a pooled ratio of totals over counties; full counts) | CDC WONDER natality |   |
| g4_fall_2024 | 4.0% | percent of 2018 births | pooled change in the count of births from 2018 to 2024 | live births to mothers aged 20 to 24 in the quarter of named counties with the largest gains that publish the band in both years | births in 2018 and 2024 |   | 145 counties | births (a pooled ratio of totals over counties; full counts) | CDC WONDER natality |   |
| g4_rise_2529 | 5.8% | percent of 2018 births | pooled change in the count of births from 2018 to 2024 | live births to mothers aged 25 to 29 in the quarter of named counties with the largest gains that publish the band in both years | births in 2018 and 2024 |   | 145 counties | births (a pooled ratio of totals over counties; full counts) | CDC WONDER natality |   |
| g4_rise_4044 | 39.3% | percent of 2018 births | pooled change in the count of births from 2018 to 2024 | live births to mothers aged 40 to 44 in the quarter of named counties with the largest gains that publish the band in both years | births in 2018 and 2024 |   | 145 counties | births (a pooled ratio of totals over counties; full counts) | CDC WONDER natality |   |
| gap_2021_q1 | 1.9 percentage points | percentage points | difference of two pooled changes in the count of births, shared bootstrap draws over counties | live births in the named counties, change from 2020 to 2021 in the least deprived quartile minus the change in the most deprived quartile | 2020 to 2021 | 95% CI 1.0 percentage points to 3.0 percentage points | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| gap_2021_q2 | 2.5 percentage points | percentage points | difference of two pooled changes in the count of births, shared bootstrap draws over counties | live births in the named counties, change from 2020 to 2021 in the second quartile minus the change in the most deprived quartile | 2020 to 2021 | 95% CI 1.4 percentage points to 3.6 percentage points | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| gap_2021_q3 | 1.3 percentage points | percentage points | difference of two pooled changes in the count of births, shared bootstrap draws over counties | live births in the named counties, change from 2020 to 2021 in the third quartile minus the change in the most deprived quartile | 2020 to 2021 | 95% CI 0.5 percentage points to 2.2 percentage points | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| gap_older_2018 | 11.3 percentage points | percentage points | difference of two pooled shares of births, shared bootstrap draws over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually; mothers aged 35 to 44; least deprived quartile minus most deprived quartile | 2018 | 95% CI 10.0 percentage points to 12.5 percentage points | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| gap_older_2024 | 12.0 percentage points | percentage points | difference of two pooled shares of births, shared bootstrap draws over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually; mothers aged 35 to 44; least deprived quartile minus most deprived quartile | 2024 | 95% CI 10.5 percentage points to 13.5 percentage points | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| gap_young_2018 | 14.0 percentage points | percentage points | difference of two pooled shares of births, shared bootstrap draws over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually; mothers aged 15 to 24; most deprived quartile minus least deprived quartile | 2018 | 95% CI 12.3 percentage points to 15.8 percentage points | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| gap_young_2024 | 12.4 percentage points | percentage points | difference of two pooled shares of births, shared bootstrap draws over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually; mothers aged 15 to 24; most deprived quartile minus least deprived quartile | 2024 | 95% CI 11.0 percentage points to 14.0 percentage points | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| group_cut_decline | 8.8% | percent of 2018 births | smallest fall among the counties in the largest-decline quarter (the group's own boundary member) | the quarter of named counties with the largest declines | births in 2018 and 2024 |   | 144 counties | none (full count) | CDC WONDER natality |   |
| group_cut_gain | 2.6% | percent of 2018 births | smallest gain among the counties in the largest-gain quarter (the group's own boundary member) | the quarter of named counties with the largest gains | births in 2018 and 2024 |   | 145 counties | none (full count) | CDC WONDER natality |   |
| group_n_largest_declines | 144 | counties | count of counties | named counties in the quarter with the largest declines in births | births in 2018 and 2024 |   |   | none (full count) | CDC WONDER natality |   |
| group_n_largest_gains | 145 | counties | count of counties | named counties in the quarter with the largest gains in births | births in 2018 and 2024 |   |   | none (full count) | CDC WONDER natality |   |
| group_total_decline | 13.5% | percent of 2018 births | fall in the pooled count of births from 2018 to 2024 | live births in the quarter of named counties with the largest declines | births in 2018 and 2024 |   |   | births (a pooled ratio of totals over counties; full counts) | CDC WONDER natality |   |
| group_total_gain | 11.2% | percent of 2018 births | rise in the pooled count of births from 2018 to 2024 | live births in the quarter of named counties with the largest gains | births in 2018 and 2024 |   |   | births (a pooled ratio of totals over counties; full counts) | CDC WONDER natality |   |
| largest_decline | 23.9% | percent of 2018 births | fall in the county's count of births from 2018 to 2024 | the named county with the largest decline (St. Louis city, MO) | births in 2018 and 2024 |   | 4,127 births | none (full count) | CDC WONDER natality |   |
| largest_gain | 67.6% | percent of 2018 births | rise in the county's count of births from 2018 to 2024 | the named county with the largest gain (Kaufman County, TX) | births in 2018 and 2024 |   | 1,786 births | none (full count) | CDC WONDER natality |   |
| map_beyond_key | 34 | counties | count of counties with a change of more than the key limit in either direction | named counties whose change is beyond the end of the map key | births in 2018 and 2024 |   | 578 counties | none (full count) | CDC WONDER natality |   |
| map_key_limit | 20 | percent of 2018 births | change in births at which the map key ends, in each direction (a display choice) | named counties on the map | births in 2018 and 2024 |   |   | none (full count) | CDC WONDER natality |   |
| min_county_births | 613 | live births | smallest annual count of births in any of the named counties | the named county-year with the fewest births | births in 2018 to 2024 |   | 4,046 county-years | none (full count) | CDC WONDER natality |   |
| named_below_threshold | one | counties | count of named counties with a 2020 Census population below the threshold | named counties outside Connecticut whose 2020 Census population is below the threshold | 2020 Census |   | 3,135 counties | none (full count) | CDC WONDER natality |   |
| pctl_5 | 5th | percentile | percentile used to describe the spread of county changes (a definition) | named counties | all years (a definition) |   |   | none (definition) | CDC WONDER natality |   |
| pctl_95 | 95th | percentile | percentile used to describe the spread of county changes (a definition) | named counties | all years (a definition) |   |   | none (definition) | CDC WONDER natality |   |
| pooled_above_threshold | 27 | counties | count of unnamed counties with a 2020 Census population of at least the threshold | counties outside Connecticut that WONDER pools although their 2020 Census population is 100,000 or more | 2020 Census |   | 3,135 counties | none (full count) | CDC WONDER natality |   |
| pooled_rows | 49 | states | count of pooled rows | states with counties below the threshold, each with one pooled Unidentified Counties row | births in 2018 to 2024 |   |   | none (full count) | CDC WONDER natality |   |
| q1_south_share | 24% | percent of counties | share in the Census South region (16 states and DC) | counties in the least deprived quartile of the named counties | births in 2018 to 2024 |   | 144 counties | none (full count) | CDC WONDER natality |   |
| q1_vs_mid_pp | 2.7 percentage points | percentage points | difference of two pooled falls in the count of births, shared bootstrap draws over counties | live births in the named counties, fall in births for the least deprived quartile minus the second and third quartiles together | births in 2018 and 2024 | 95% CI −0.5 percentage points to 5.9 percentage points | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| q4_midwest | 9.2% | percent of 2018 births | fall in the pooled count of births from 2018 to 2024, bootstrap interval over counties | live births in the most deprived quartile of the named counties in the Census Midwest region | births in 2018 and 2024 | 95% CI 6.3% to 11.6% | 53 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| q4_northeast | 9.3% | percent of 2018 births | fall in the pooled count of births from 2018 to 2024, bootstrap interval over counties | live births in the most deprived quartile of the named counties in the Census Northeast region | births in 2018 and 2024 | 95% CI 6.6% to 11.8% | 22 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| q4_south | 5.0% | percent of 2018 births | fall in the pooled count of births from 2018 to 2024, bootstrap interval over counties | live births in the most deprived quartile of the named counties in the Census South region | births in 2018 and 2024 | 95% CI 2.9% to 7.0% | 65 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| q4_south_share | 45% | percent of counties | share in the Census South region (16 states and DC) | counties in the most deprived quartile of the named counties | births in 2018 to 2024 |   | 145 counties | none (full count) | CDC WONDER natality |   |
| q4_vs_mid_pp | 4.5 percentage points | percentage points | difference of two pooled falls in the count of births, shared bootstrap draws over counties | live births in the named counties, fall in births for the most deprived quartile minus the second and third quartiles together | births in 2018 and 2024 | 95% CI 2.3 percentage points to 6.7 percentage points | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| q4_vs_q1_pp | 1.7 percentage points | percentage points | difference of two pooled falls in the count of births, shared bootstrap draws over counties | live births in the named counties, fall in births for the most deprived quartile minus the least deprived quartile | births in 2018 and 2024 | 95% CI −1.2 percentage points to 5.0 percentage points | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| q4_west | 9.3% | percent of 2018 births | fall in the pooled count of births from 2018 to 2024; no interval, because the cell holds fewer than 10 counties (all of them lost births) | live births in the most deprived quartile of the named counties in the Census West region | births in 2018 and 2024 |   | 5 counties | births (a pooled ratio of totals over counties; full counts) | CDC WONDER natality |   |
| q4_west_n | 5 | counties | count of counties | counties in the most deprived quartile of the named counties in the Census West region | births in 2018 to 2024 |   |   | none (full count) | CDC WONDER natality |   |
| region_midwest | −8.4% | percent of 2018 births | pooled change in the count of births from 2018 to 2024, bootstrap interval over counties | live births in the named counties in the Census Midwest region | births in 2018 and 2024 | 95% CI −10.4% to −6.3% | 137 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| region_northeast | −5.0% | percent of 2018 births | pooled change in the count of births from 2018 to 2024, bootstrap interval over counties | live births in the named counties in the Census Northeast region | births in 2018 and 2024 | 95% CI −7.3% to −2.5% | 110 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| region_south | 0.0% | percent of 2018 births | pooled change in the count of births from 2018 to 2024, bootstrap interval over counties | live births in the named counties in the Census South region | births in 2018 and 2024 | 95% CI −1.7% to 1.8% | 232 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| region_west | −7.9% | percent of 2018 births | pooled change in the count of births from 2018 to 2024, bootstrap interval over counties | live births in the named counties in the Census West region | births in 2018 and 2024 | 95% CI −10.7% to −5.0% | 99 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| rise_2024 | 0.9% | percent of 2023 births | rise in the count of births from 2023 to 2024 | live births in the counties that CDC WONDER natality identifies in every year (counties with 100,000 or more residents in the population vintage WONDER uses) | 2023 to 2024 |   |   | none (full count) | CDC WONDER natality |   |
| rise_3539 | 9.2% | percent of 2018 births | pooled change in the count of births from 2018 to 2024, bootstrap interval over counties | live births to mothers aged 35 to 39 in the named counties that publish the band in both years | births in 2018 and 2024 | 95% CI 7.3% to 11.0% | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| rise_4044 | 19.5% | percent of 2018 births | pooled change in the count of births from 2018 to 2024, bootstrap interval over counties | live births to mothers aged 40 to 44 in the named counties that publish the band in both years | births in 2018 and 2024 | 95% CI 17.0% to 22.3% | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| rise_older_diff | 0.7 percentage points | percentage points | difference of two changes in pooled shares: rise in the share of births to mothers aged 35 to 44, least deprived quartile minus most deprived quartile, shared bootstrap draws over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually | births in 2018 and 2024 | 95% CI 0.3 percentage points to 1.2 percentage points | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| rise_older_q1 | 3.5 percentage points | percentage points | change from 2018 to 2024 in the pooled share of births, shared bootstrap draws over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually; mothers aged 35 to 44; least deprived quartile | births in 2018 and 2024 | 95% CI 3.1 percentage points to 3.9 percentage points | 144 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| rise_older_q4 | 2.8 percentage points | percentage points | change from 2018 to 2024 in the pooled share of births, shared bootstrap draws over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually; mothers aged 35 to 44; most deprived quartile | births in 2018 and 2024 | 95% CI 2.5 percentage points to 3.1 percentage points | 145 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| rise_share_older | 3.2 percentage points | percentage points | change from 2018 to 2024 in the pooled share of births, shared bootstrap draws over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually, births in published cells; mothers aged 35 to 44 | births in 2018 and 2024 | 95% CI 3.1 percentage points to 3.4 percentage points | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| share_declined | 65.7% | percent of named counties | share of counties with fewer births in 2024 than in 2018 | named counties | births in 2018 and 2024 |   | 578 counties | none (full count) | CDC WONDER natality |   |
| share_named_2018 | 79.7% | percent of live births in the United States | share of births in the named counties | live births in the 50 states and DC | 2018 |   |   | none (full count) | CDC WONDER natality |   |
| share_named_2024 | 79.4% | percent of live births in the United States | share of births in the named counties | live births in the 50 states and DC | 2024 |   |   | none (full count) | CDC WONDER natality |   |
| share_older_2018 | 19.7% | percent of live births to mothers aged 15 to 44 | pooled share of births in published cells, bootstrap interval over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually, births in published cells; mothers aged 35 to 44 | 2018 | 95% CI 18.9% to 20.5% | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| share_older_2024 | 22.9% | percent of live births to mothers aged 15 to 44 | pooled share of births in published cells, bootstrap interval over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually, births in published cells; mothers aged 35 to 44 | 2024 | 95% CI 22.1% to 23.8% | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| share_older_q1_2018 | 24.3% | percent of live births to mothers aged 15 to 44 | pooled share of births in published cells, bootstrap interval over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually in the least deprived quartile of counties by deprivation rank, mothers aged 35 to 44 | 2018 | 95% CI 23.1% to 25.5% | 144 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| share_older_q1_2024 | 27.8% | percent of live births to mothers aged 15 to 44 | pooled share of births in published cells, bootstrap interval over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually in the least deprived quartile of counties by deprivation rank, mothers aged 35 to 44 | 2024 | 95% CI 26.4% to 29.2% | 144 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| share_older_q4_2018 | 13.0% | percent of live births to mothers aged 15 to 44 | pooled share of births in published cells, bootstrap interval over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually in the most deprived quartile of counties by deprivation rank, mothers aged 35 to 44 | 2018 | 95% CI 12.5% to 13.5% | 145 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| share_older_q4_2024 | 15.8% | percent of live births to mothers aged 15 to 44 | pooled share of births in published cells, bootstrap interval over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually in the most deprived quartile of counties by deprivation rank, mothers aged 35 to 44 | 2024 | 95% CI 15.1% to 16.5% | 145 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| share_young_2018 | 21.8% | percent of live births to mothers aged 15 to 44 | pooled share of births in published cells, bootstrap interval over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually, births in published cells; mothers aged 15 to 24 | 2018 | 95% CI 21.0% to 22.7% | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| share_young_2024 | 18.7% | percent of live births to mothers aged 15 to 44 | pooled share of births in published cells, bootstrap interval over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually, births in published cells; mothers aged 15 to 24 | 2024 | 95% CI 18.0% to 19.5% | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| share_young_q1_2018 | 17.0% | percent of live births to mothers aged 15 to 44 | pooled share of births in published cells, bootstrap interval over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually in the least deprived quartile of counties by deprivation rank, mothers aged 15 to 24 | 2018 | 95% CI 15.6% to 18.3% | 144 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| share_young_q1_2024 | 14.5% | percent of live births to mothers aged 15 to 44 | pooled share of births in published cells, bootstrap interval over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually in the least deprived quartile of counties by deprivation rank, mothers aged 15 to 24 | 2024 | 95% CI 13.4% to 15.5% | 144 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| share_young_q4_2018 | 30.9% | percent of live births to mothers aged 15 to 44 | pooled share of births in published cells, bootstrap interval over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually in the most deprived quartile of counties by deprivation rank, mothers aged 15 to 24 | 2018 | 95% CI 29.9% to 32.1% | 145 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| share_young_q4_2024 | 26.9% | percent of live births to mothers aged 15 to 44 | pooled share of births in published cells, bootstrap interval over counties | live births to mothers aged 15 to 44 in the counties that CDC WONDER natality names individually in the most deprived quartile of counties by deprivation rank, mothers aged 15 to 24 | 2024 | 95% CI 25.8% to 28.0% | 145 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| slope_u | −0.7 percentage points | percentage points of change in births per ten points of county deprivation rank | slope of the county change in births (percent) on county Area Deprivation Index rank, unweighted, one county one count, bootstrap interval over counties | named counties | births in 2018 and 2024 | 95% CI −1.1 percentage points to −0.3 percentage points | 578 counties | none (each county counts once) | CDC WONDER natality |   |
| slope_w | +0.5 percentage points | percentage points of change in births per ten points of county deprivation rank | slope of the county change in births (percent) on county Area Deprivation Index rank, weighted by 2018 births, bootstrap interval over counties | named counties | births in 2018 and 2024 | 95% CI −0.2 percentage points to 1.2 percentage points | 578 counties | 2018 births | CDC WONDER natality |   |
| south_counties | 232 | counties | count of counties | named counties in the Census South region (16 states and DC) | births in 2018 to 2024 |   |   | none (full count) | CDC WONDER natality |   |
| south_minus_midwest | 8.4 percentage points | percentage points | difference of two pooled changes in the count of births, shared bootstrap draws over counties | live births in the named counties, South minus Midwest | births in 2018 and 2024 | 95% CI 5.7 percentage points to 11.1 percentage points | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| south_minus_northeast | 5.0 percentage points | percentage points | difference of two pooled changes in the count of births, shared bootstrap draws over counties | live births in the named counties, South minus Northeast | births in 2018 and 2024 | 95% CI 2.0 percentage points to 7.9 percentage points | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| south_minus_west | 7.9 percentage points | percentage points | difference of two pooled changes in the count of births, shared bootstrap draws over counties | live births in the named counties, South minus West | births in 2018 and 2024 | 95% CI 4.3 percentage points to 11.3 percentage points | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| south_q123 | +1.1% | percent of 2018 births | pooled change in the count of births from 2018 to 2024, bootstrap interval over counties | live births in the three less deprived quartiles of the named counties in the Census South region | births in 2018 and 2024 | 95% CI −0.9% to 3.4% | 167 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| south_q4_gap | 6.1 percentage points | percentage points | difference of two pooled changes in the count of births, shared bootstrap draws over counties | live births in the named counties in the Census South region, three less deprived quartiles minus the most deprived | births in 2018 and 2024 | 95% CI 3.2 percentage points to 9.0 percentage points | 578 counties | births in each county (a pooled ratio of sums over counties); interval from a bootstrap over counties | CDC WONDER natality |   |
| south_share | 40.1% | percent of named counties | share of named counties in the Census South region (16 states and DC) | named counties | births in 2018 to 2024 |   | 578 counties | none (full count) | CDC WONDER natality |   |
| south_states | 16 | states | states in the Census South region, besides the District of Columbia (a definition) | states | all years (a definition) |   |   | none (definition) | CDC WONDER natality |   |
| ss_actual_p5 | 16.6% | percent of 2018 births | fall in the county's births to mothers aged 15 to 44, 5th percentile across counties | named counties at the 5th percentile of change in births to mothers aged 15 to 44 | births in 2018 and 2024 |   | 577 counties | none (full count) | CDC WONDER natality |   |
| ss_actual_p95 | 19.8% | percent of 2018 births | gain in the county's births to mothers aged 15 to 44, 95th percentile across counties | named counties at the 95th percentile of change in births to mothers aged 15 to 44 | births in 2018 and 2024 |   | 577 counties | none (full count) | CDC WONDER natality |   |
| ss_corr_u | −0.03 | correlation coefficient | correlation, unweighted, one county one count, between the change in births that a county's 2018 age mix implies (each band changing at the all-county rate) and its change; county-cluster bootstrap interval | named counties that publish all six age bands in 2018 and 2024 | births in 2018 and 2024 | 95% CI −0.11 to 0.04 | 577 counties | none (each county counts once) | CDC WONDER natality |   |
| ss_corr_w | −0.16 | correlation coefficient | correlation, weighted by 2018 births to mothers aged 15 to 44, between the change in births that a county's 2018 age mix implies (each band changing at the all-county rate) and its change; county-cluster bootstrap interval | named counties that publish all six age bands in 2018 and 2024 | births in 2018 and 2024 | 95% CI −0.26 to −0.06 | 577 counties | 2018 births to mothers aged 15 to 44 | CDC WONDER natality |   |
| ss_counties | 577 | counties | count of counties | named counties that publish all six age bands in 2018 and 2024 | births in 2018 and 2024 |   |   | none (full count) | CDC WONDER natality |   |
| ss_implied_p5 | 8.9% | percent of 2018 births | fall implied by the county's 2018 age mix, 5th percentile across counties | named counties at the 5th percentile of implied change | births in 2018 and 2024 |   | 577 counties | none (full count) | CDC WONDER natality |   |
| ss_implied_p95 | 1.3% | percent of 2018 births | fall implied by the county's 2018 age mix, 95th percentile across counties | named counties at the 95th percentile of implied change | births in 2018 and 2024 |   | 577 counties | none (full count) | CDC WONDER natality |   |
| ss_left_out | one | counties | count of counties left out of the shift-share check | named counties with a withheld age cell in 2018 or 2024 | births in 2018 and 2024 |   |   | none (full count) | CDC WONDER natality |   |
| tail_cells | 12,138 | cells | count of cells | county-year-by-age cells for mothers under 15 and 45 and over in the named counties | births in 2018 to 2024 |   |   | none (full count) | CDC WONDER natality |   |
| tail_published_share | 0.26% | percent of live births | share of those births to mothers under 15 or 45 and over, in published cells | live births in the published age-of-mother cells of the named counties | births in 2018 to 2024 |   |   | none (full count) | CDC WONDER natality |   |
| tail_withheld_cells | 6,594 | cells | count of cells with 1 to 9 births, which WONDER withholds | county-year-by-age cells for mothers under 15 and 45 and over in the named counties | births in 2018 to 2024 |   |   | none (full count) | CDC WONDER natality |   |
| tail_withheld_max_share | 0.29% | percent of live births | largest share of births the withheld tail cells could hold: 9 births in each, over births in published cells | live births in the published age-of-mother cells of the named counties | births in 2018 to 2024 |   |   | none (full count) | CDC WONDER natality |   |
| thin_cell_limit | 10 | counties | fewest counties for which a bootstrap interval over counties is printed (the library's minimum number of clusters) | cells of the region-by-quartile figure | births in 2018 and 2024 |   |   | none (full count) | CDC WONDER natality |   |
| top_tenth_cut | 10.2% | percent of 2018 births | gain at the 90th percentile of the county changes in births | named counties | births in 2018 and 2024 |   | 578 counties | none (full count) | CDC WONDER natality |   |
| top_tenth_n | 58 | counties | count of counties at or above the 90th percentile of change | named counties in the top tenth of change in births | births in 2018 and 2024 |   |   | none (full count) | CDC WONDER natality |   |
| top_tenth_other_max | 5 | counties | largest count of those counties in any state other than Texas and Florida | named counties in the top tenth of change, in the state with the next most | births in 2018 and 2024 |   |   | none (full count) | CDC WONDER natality |   |
| top_tenth_south | 43 | counties | count of those counties in the Census South region (16 states and DC) | named counties in the top tenth of change that are in the Census South region | births in 2018 and 2024 |   |   | none (full count) | CDC WONDER natality |   |
| top_tenth_texas | 12 | counties | count of those counties in Texas, which equals the count in Florida (asserted in the build) | named counties in the top tenth of change that are in Texas, a count that Florida also has | births in 2018 and 2024 |   |   | none (full count) | CDC WONDER natality |   |
| us_births_2018 | 3.79 million | live births | count of live births | live births in the 50 states and DC | 2018 |   |   | none (full count) | CDC WONDER natality |   |
| us_births_2024 | 3.63 million | live births | count of live births | live births in the 50 states and DC | 2024 |   |   | none (full count) | CDC WONDER natality |   |
| wonder_suppression_floor | 10 | births | a cell with fewer births than this is withheld (a definition) | cells of the WONDER natality files | births in 2018 to 2024 |   |   | none (definition) | CDC WONDER natality |   |
| wonder_threshold | 100,000 | residents | population size at which WONDER identifies a county, applied to an earlier population vintage than the 2020 census (a definition) | counties that CDC WONDER natality identifies | births in 2018 to 2024 |   |   | none (definition) | CDC WONDER natality |   |

## Definitions

- Bootstrap interval: A range for an estimate found by recomputing it on many random resamples of the data and reading the range from the results. It shows how much the estimate would vary from sample to sample.
- Area Deprivation Index (ADI): A score that ranks neighborhoods by income, education, employment and housing conditions drawn from the American Community Survey. In this book a higher national percentile means a more deprived neighborhood.
- Population-weighted: Averaged so that each place counts in proportion to its number of residents, which lets a large county move the result more than a small one. An unweighted average counts every place equally.
- Suppression: The withholding of a number because the count behind it is too small to publish without risking the identification of a person. A suppressed value is missing, not zero.
- Ecological inference: Drawing conclusions about individuals from data about places or groups. A pattern across counties need not hold for the people inside them.

## Methods

This chapter compares births from 2018 to 2024 across the 578 counties that CDC WONDER names individually in every year, a set chosen by population size in a vintage earlier than the 2020 Census and not by outcome, and across groups of those counties by deprivation quartile and region. The figures are counts and shares of births, not birth rates, because no file used here holds women by age for counties, and births by mother's age use six of nine bands because most cells of the youngest and oldest bands are withheld. Pooled changes weight each county by its births, and counties that WONDER pools into an Unidentified Counties row have no county value. Births are full counts, so the intervals show dependence on which counties are in a group and not sampling error.

### Which births and counties are used

Births are counts from CDC WONDER natality for 2018 to 2024 (2024 is final), by county of the mother's residence. The 578 named counties are the counties that WONDER identifies in every year and that have births in every year: counties with 100,000 or more residents in the population vintage WONDER uses, which is earlier than the 2020 Census. By 2020 Census population 27 counties outside Connecticut that have 100,000 or more residents are still pooled, and one named county is below it.

WONDER pools every other county in a state into one Unidentified Counties row (49 rows), which is used only for the comparison of the named counties with the rest of the country. WONDER lists two further identifiers in every year with no births (Cape May County NJ, Portsmouth city VA), which are left out. The panel is defined by size, not by outcome, and every named county appears in all seven years. County totals have no withheld cell.

Explains Table 1 and Table 2.

### How births by mother's age and withheld cells are handled

Births by mother's age come in nine bands. WONDER withholds cells of 1 to 9 births. A withheld cell is missing: it leaves the numerator and the denominator, which is the births in the published cells, and nothing is derived from a county total minus the published cells.

The six bands from 15 to 19 through 40 to 44 have 11 withheld cells of 24,276, which could hold at most 99 births. The under-15 band and the 45-and-over bands are left out because most of their cells are withheld (6,594 of 12,138); the published tail cells hold 0.26% of births and the withheld ones at most 0.29%.

A share is the births to mothers in an age range over births in the published cells for mothers aged 15 to 44, pooled over counties. A change in a band compares the counties that publish the band in both 2018 and 2024. No rate is computed: no file used here holds women by age for counties.

The shift-share check applies the all-county change of each age band to each county's 2018 age mix and correlates the implied change with the observed change in births to mothers aged 15 to 44.

Explains Table 6, Table 7 and Table 8.

### How counties are ranked, grouped and weighted

A tract's Area Deprivation Index national rank is the unweighted mean of the ranks of its block groups. A county's deprivation rank is the mean of its tracts' ranks weighted by 2019-2023 tract population, with Connecticut tracts assigned to the eight legacy counties; quartiles hold equal numbers of the named counties. Regions are the four Census Bureau regions (the South has 16 states and DC).

Pooled changes, shares and differences are ratios of sums over counties, so they weight each county by its births.

The map draws every county of the book's county map; counties that WONDER does not name have no value.

Explains Table 4, Table 5 and Table 2.

### What the intervals do and do not show

Births are full counts, so these intervals show dependence on which counties are in a group and not sampling error. A region-by-quartile cell with fewer than 10 counties shows no interval, because a bootstrap over so few counties is mechanical. The groups of counties formed by the change in total births are defined on the outcome and carry no interval.

### How the bootstrap intervals are computed

Pooled changes, shares and differences carry 95% percentile intervals from a bootstrap that resamples whole counties (2,000 replicates, seed 12345), with the same draws for every statistic so that a difference has its own interval. Correlations and slopes use a county-cluster bootstrap.

## What these data cannot show

The chapter reports counts and shares of births and no rates. A birth rate needs the number of women of each age as its denominator, and the files staged for this book hold the total population of counties and tracts but not women by age. A fall in births to mothers aged 20 to 24 can mean fewer births per woman, fewer women in that age group, or both, and so can a gain. County population estimates by age and sex from the Census Bureau would supply the denominator for age-specific rates. Births are counted in the mother's county of residence, so the map is not a map of fertility.

County results describe the 578 counties that WONDER identifies, those with 100,000 or more residents in its population vintage. They hold 79.4% of births in 2024, and they are not a sample of the country. The pooled rows lost fewer births, although those rows include counties that now exceed the line. WONDER's county files used here have no cut by the mother's race or Hispanic origin, so the chapter cannot say whether the shift in mothers' ages differs by group.

The deprivation comparison is descriptive. The Area Deprivation Index describes neighborhoods in 2019 to 2023 and is averaged to counties, and region and deprivation overlap. The comparison of quartiles says nothing about why births fell in any county. It is an ecological pattern, and it need not hold for the people inside the counties. The comparison of 2018 with 2024 uses the endpoint years only. A county with few births moves from year to year by chance, so a county's direction of change is better established than its rank among the named counties.

## References

1. Osterman, Michelle J. K.; Hamilton, Brady E.; Martin, Joyce A.; Driscoll, Anne K.; Valenzuela, Claudia P. (2026). Births: Final Data for 2024. National Vital Statistics Reports 75(2). https://doi.org/10.15620/cdc/252440
2. Kearney, Melissa S.; Levine, Phillip B.; Pardue, Luke (2022). The Puzzle of Falling US Birth Rates since the Great Recession. Journal of Economic Perspectives 36(1): 151-176. https://doi.org/10.1257/jep.36.1.151
3. Kind, Amy J. H.; Buckingham, William R. (2018). Making Neighborhood-Disadvantage Metrics Accessible: The Neighborhood Atlas. New England Journal of Medicine 378(26): 2456-2458. https://doi.org/10.1056/NEJMp1802313
4. Mathews, T. J.; Hamilton, Brady E. (2016). Mean Age of Mothers is on the Rise: United States, 2000-2014. NCHS Data Brief No. 232. https://www.cdc.gov/nchs/products/databriefs/db232.htm

## Provenance

- Pipeline version: 0.1.0
- Build script: book2/chapters/where-births-are-falling/build.py (sha256 b47a334b398b4f7778e70d1b6a0a82dd6de30eed8a68b4e929b8ed5020155bf4)
- Built on: 2026-10-09
- Site commit: c2b1ff3309cb4a10833f884da91ac0057a66ad0a

Inputs:

| File | Size (bytes) | SHA-256, first 1 MB | SHA-256, last 1 MB |
| --- | ---: | --- | --- |
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| data/analytic/tract_atlas.parquet | 39,659,925 | 29d5e4d943552d54aeb6ba92aadc939d9bd15bdea553c78357dbd516757be627 | 1e10d1ecf722340f23ee2212d4999a90250f85b65fa89b39e32db06d9472e22e |
| data/staged/births/wonder_natality_county_age_of_mother_2018_2024.parquet | 99,054 | b31e8b07c5eab8e54c94c4b57e7100327bf4dd6058d309cf128c3e4c640e44de | b31e8b07c5eab8e54c94c4b57e7100327bf4dd6058d309cf128c3e4c640e44de |
| data/staged/births/wonder_natality_county_total_2018_2024.parquet | 41,774 | e85d351fa72c022a05415d332185113b6badcaff1119da1d6f45c76ffe16d86d | e85d351fa72c022a05415d332185113b6badcaff1119da1d6f45c76ffe16d86d |
| data/staged/crosswalks/ct_tract2020_to_old_county.parquet | 15,842 | 961ef39f31596ef65fca2c67d5f2f63e533c5dc9b49745d3bb6437844e4b831d | 961ef39f31596ef65fca2c67d5f2f63e533c5dc9b49745d3bb6437844e4b831d |

Outputs:

| File | SHA-256 |
| --- | --- |
| facts.json | 77dd7eeea51784d62bbc66c924c5860689674d3033447c7880a586600453d9d5 |
| figures/age_change_by_county_change.json | 826d10c0a72167e0dbc41166ca2774d1d5c1d8c76df276e0ba5c2e42c6a52c4e |
| figures/births_by_deprivation.json | a21507843ebed1ddc8e6328285a33c0c9239ee6232858f469a4f30a9ae0e438e |
| figures/births_by_mother_age.json | 08b341775c96401ffd6ff6bf57bbe64d8290d998ed1ed855be2d5eea3e3d26a1 |
| figures/births_change_extremes.json | b625f3ef03d0e5fe62215d49d4651873e4e901ed120902c74d870f7819eeb14a |
| figures/births_change_map.json | 56281bbfe963990b15b8a6077266a4261a7dab56d91f830f4c6db01d66e89338 |
| figures/births_change_region_quartile.json | 056abf936ea3e1c4c3f5cfb66aeb3bf3434baee4c2b9d7cf2397c50dc584dd7b |
| figures/births_trend.json | 245d4e7aa4082510358d578cd02c61ee0e58cc2ed2b5d567605029bc48714694 |
| figures/mother_age_by_deprivation.json | a38297d682101f0ebc324d312b77f965d35e255e15d478ba0ea693591638de14 |
| meta.json | 78f25853ee414eae541cc5f9ab5f47a727040344922c9465602efd30b8f951ee |
| public/data/where-births-are-falling/births_change_map.json | 9751a5d7cca25f7381cc4799d7262211ddee3ea0e1182d31d8f3646e39d6238b |
| refs.json | 8ce76203656a29a39f6fa686e3886d08269b60425bc06bce02adb1cedd12496b |

## Machine formats

- Report (HTML): https://vishalsingh.org/zipcode/where-births-are-falling/report
- Report (Markdown): https://vishalsingh.org/zipcode/where-births-are-falling/report.md
- Every estimate (JSON): https://vishalsingh.org/zipcode/report/where-births-are-falling/facts.json
- Table 1, figure "births_trend" (JSON): https://vishalsingh.org/zipcode/report/where-births-are-falling/figures/births_trend.json
- Table 2, figure "births_change_map" (JSON): https://vishalsingh.org/zipcode/report/where-births-are-falling/figures/births_change_map.json
- Table 3, figure "births_change_extremes" (JSON): https://vishalsingh.org/zipcode/report/where-births-are-falling/figures/births_change_extremes.json
- Table 4, figure "births_by_deprivation" (JSON): https://vishalsingh.org/zipcode/report/where-births-are-falling/figures/births_by_deprivation.json
- Table 5, figure "births_change_region_quartile" (JSON): https://vishalsingh.org/zipcode/report/where-births-are-falling/figures/births_change_region_quartile.json
- Table 6, figure "births_by_mother_age" (JSON): https://vishalsingh.org/zipcode/report/where-births-are-falling/figures/births_by_mother_age.json
- Table 7, figure "mother_age_by_deprivation" (JSON): https://vishalsingh.org/zipcode/report/where-births-are-falling/figures/mother_age_by_deprivation.json
- Table 8, figure "age_change_by_county_change" (JSON): https://vishalsingh.org/zipcode/report/where-births-are-falling/figures/age_change_by_county_change.json
- Payload of "births_change_map" (JSON): https://vishalsingh.org/zipcode/data/where-births-are-falling/births_change_map.json
- Index of every report: https://vishalsingh.org/zipcode/llms.txt; all reports in one file: https://vishalsingh.org/zipcode/llms-full.txt