{
  "alt": "Line chart of the internal consistency of the two indices in each ANES study from 1984 to 2024. Both lines start low in the 1980s, with the cultural index lower, and dip in studies where an index has only two items, which are shaded. The economic index climbs to a peak of {fact:alpha_econ_2020} in 2020 and is {fact:alpha_econ_2024} in 2024; the cultural index reaches {fact:alpha_cult_2024} in 2024.",
  "caption": "Alpha is higher in recent studies for both indices: the economic index went from {fact:alpha_econ_1984} in 1984 to a peak of {fact:alpha_econ_2020} in 2020 and {fact:alpha_econ_2024} in 2024, and the cultural index from {fact:alpha_cult_1988} in 1988, the first study with three cultural items, to {fact:alpha_cult_2024} in 2024. Alpha runs from zero, when the items are unrelated, to one, when they agree perfectly. Values are lower in the shaded studies, where an index has only two items.",
  "data": [
    {
      "conf_high": 0.656085,
      "conf_low": 0.529767,
      "estimate": 0.600793,
      "items": 3,
      "n": 629,
      "series": "Economic index",
      "year": 1984
    },
    {
      "conf_high": 0.511476,
      "conf_low": 0.325173,
      "estimate": 0.426258,
      "items": 2,
      "n": 914,
      "series": "Economic index",
      "year": 1986
    },
    {
      "conf_high": 0.657749,
      "conf_low": 0.571494,
      "estimate": 0.618026,
      "items": 3,
      "n": 1171,
      "series": "Economic index",
      "year": 1988
    },
    {
      "conf_high": 0.560821,
      "conf_low": 0.372618,
      "estimate": 0.474335,
      "items": 2,
      "n": 729,
      "series": "Economic index",
      "year": 1990
    },
    {
      "conf_high": 0.658085,
      "conf_low": 0.586459,
      "estimate": 0.624958,
      "items": 3,
      "n": 1588,
      "series": "Economic index",
      "year": 1992
    },
    {
      "conf_high": 0.710332,
      "conf_low": 0.628415,
      "estimate": 0.672281,
      "items": 3,
      "n": 1451,
      "series": "Economic index",
      "year": 1994
    },
    {
      "conf_high": 0.707379,
      "conf_low": 0.621295,
      "estimate": 0.664979,
      "items": 3,
      "n": 1185,
      "series": "Economic index",
      "year": 1996
    },
    {
      "conf_high": 0.550047,
      "conf_low": 0.371641,
      "estimate": 0.466417,
      "items": 2,
      "n": 1055,
      "series": "Economic index",
      "year": 1998
    },
    {
      "conf_high": 0.660754,
      "conf_low": 0.529921,
      "estimate": 0.600034,
      "items": 3,
      "n": 675,
      "series": "Economic index",
      "year": 2000
    },
    {
      "conf_high": 0.734477,
      "conf_low": 0.638891,
      "estimate": 0.689364,
      "items": 3,
      "n": 832,
      "series": "Economic index",
      "year": 2004
    },
    {
      "conf_high": 0.770321,
      "conf_low": 0.678617,
      "estimate": 0.726017,
      "items": 3,
      "n": 765,
      "series": "Economic index",
      "year": 2008
    },
    {
      "conf_high": 0.780638,
      "conf_low": 0.744151,
      "estimate": 0.762471,
      "items": 3,
      "n": 4486,
      "series": "Economic index",
      "year": 2012
    },
    {
      "conf_high": 0.806581,
      "conf_low": 0.769528,
      "estimate": 0.788587,
      "items": 3,
      "n": 2772,
      "series": "Economic index",
      "year": 2016
    },
    {
      "conf_high": 0.844449,
      "conf_low": 0.821398,
      "estimate": 0.833273,
      "items": 3,
      "n": 5691,
      "series": "Economic index",
      "year": 2020
    },
    {
      "conf_high": 0.811195,
      "conf_low": 0.773334,
      "estimate": 0.792751,
      "items": 3,
      "n": 3743,
      "series": "Economic index",
      "year": 2024
    },
    {
      "conf_high": 0.408688,
      "conf_low": 0.281128,
      "estimate": 0.35163,
      "items": 2,
      "n": 1508,
      "series": "Cultural index",
      "year": 1984
    },
    {
      "conf_high": 0.441569,
      "conf_low": 0.286578,
      "estimate": 0.370249,
      "items": 2,
      "n": 914,
      "series": "Cultural index",
      "year": 1986
    },
    {
      "conf_high": 0.493603,
      "conf_low": 0.382216,
      "estimate": 0.439784,
      "items": 3,
      "n": 1462,
      "series": "Cultural index",
      "year": 1988
    },
    {
      "conf_high": 0.287822,
      "conf_low": 0.0366212,
      "estimate": 0.173161,
      "items": 2,
      "n": 729,
      "series": "Cultural index",
      "year": 1990
    },
    {
      "conf_high": 0.557562,
      "conf_low": 0.481545,
      "estimate": 0.522897,
      "items": 3,
      "n": 1900,
      "series": "Cultural index",
      "year": 1992
    },
    {
      "conf_high": 0.567093,
      "conf_low": 0.475074,
      "estimate": 0.526825,
      "items": 3,
      "n": 1582,
      "series": "Cultural index",
      "year": 1994
    },
    {
      "conf_high": 0.602352,
      "conf_low": 0.513385,
      "estimate": 0.559431,
      "items": 3,
      "n": 1346,
      "series": "Cultural index",
      "year": 1996
    },
    {
      "conf_high": 0.602481,
      "conf_low": 0.505554,
      "estimate": 0.557495,
      "items": 3,
      "n": 989,
      "series": "Cultural index",
      "year": 1998
    },
    {
      "conf_high": 0.567428,
      "conf_low": 0.428675,
      "estimate": 0.50198,
      "items": 3,
      "n": 759,
      "series": "Cultural index",
      "year": 2000
    },
    {
      "conf_high": 0.656418,
      "conf_low": 0.56639,
      "estimate": 0.614368,
      "items": 3,
      "n": 971,
      "series": "Cultural index",
      "year": 2004
    },
    {
      "conf_high": 0.63881,
      "conf_low": 0.519646,
      "estimate": 0.58455,
      "items": 3,
      "n": 924,
      "series": "Cultural index",
      "year": 2008
    },
    {
      "conf_high": 0.645937,
      "conf_low": 0.599319,
      "estimate": 0.622978,
      "items": 3,
      "n": 5118,
      "series": "Cultural index",
      "year": 2012
    },
    {
      "conf_high": 0.665714,
      "conf_low": 0.613877,
      "estimate": 0.641652,
      "items": 3,
      "n": 3251,
      "series": "Cultural index",
      "year": 2016
    },
    {
      "conf_high": 0.710389,
      "conf_low": 0.675277,
      "estimate": 0.69289,
      "items": 3,
      "n": 6354,
      "series": "Cultural index",
      "year": 2020
    },
    {
      "conf_high": 0.717904,
      "conf_low": 0.671219,
      "estimate": 0.694374,
      "items": 3,
      "n": 4109,
      "series": "Cultural index",
      "year": 2024
    }
  ],
  "id": "reliability",
  "notes": [
    "Alpha uses adults who answered every item of the index that year.",
    "Shaded studies have only two items on one or both indices: the cultural index in 1984, both indices in 1986 and 1990, and the economic index in 1998."
  ],
  "source": "ANES Cumulative Data File, 1984 to 2024; weighted (VCF0009z); intervals are model based",
  "spec": {
    "annotations": [
      {
        "type": "band",
        "x1": 1983.4,
        "x2": 1984.6
      },
      {
        "type": "band",
        "x1": 1985.4,
        "x2": 1986.6
      },
      {
        "type": "band",
        "x1": 1989.4,
        "x2": 1990.6
      },
      {
        "type": "band",
        "x1": 1997.4,
        "x2": 1998.6
      }
    ],
    "colors": {
      "Cultural index": "cat2",
      "Economic index": "cat1"
    },
    "hi": "conf_high",
    "lo": "conf_low",
    "n": "n",
    "series": "series",
    "x": "year",
    "xDomain": [
      1982,
      2026
    ],
    "xLabel": "ANES study year",
    "y": "estimate",
    "yDomain": [
      0,
      1
    ],
    "yFormat": {
      "digits": 1
    },
    "yLabel": "Standardized Cronbach alpha"
  },
  "subtitle": "Standardized Cronbach alpha of each index by ANES study, adults who answered every item of the index that year, 1984 to 2024; 95% intervals from resampling respondents",
  "table": {
    "columns": [
      {
        "key": "year",
        "label": "Study"
      },
      {
        "key": "series",
        "label": "Index"
      },
      {
        "format": {
          "digits": 2
        },
        "key": "estimate",
        "label": "Alpha"
      },
      {
        "format": {
          "digits": 2
        },
        "key": "conf_low",
        "label": "Interval low"
      },
      {
        "format": {
          "digits": 2
        },
        "key": "conf_high",
        "label": "Interval high"
      },
      {
        "format": {
          "digits": 0,
          "thousands": true
        },
        "key": "n",
        "label": "Respondents with every item"
      },
      {
        "format": {
          "digits": 0
        },
        "key": "items",
        "label": "Items in the index"
      }
    ]
  },
  "title": "Items in each index agree more in recent studies, and the cultural items agree less than the economic items in {fact:n_cult_lower} of {fact:n_studies} studies",
  "type": "line",
  "width": "body"
}