Republican share of the two-party vote, 2020 and Average test score
Where Republican share of the two-party vote, 2020 is higher, Average test score tends to be higher. The link is moderate: +0.52 across 2,740 counties, on a scale from −1 (opposite) to +1 (in step). That figure compares places with the same population density, income and education, so those differences can't explain it. It holds inside states too. Measured separately within each of 38 states, the middle value of the link is +0.07.
Holds after adjusting
Every place, plotted
One dot for each place reporting both measures. Hover over or tap a dot to see its name and values. The thin line is the straight line that best fits the dots. The bold line, shown for counties, is the link after adjusting for density, income and education. A dot far from the lines is a place that does not follow the pattern.
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What each measure is
Republican share of the two-party vote, 2020
The Republican share of the votes for the two main parties in the 2020 presidential election. It is shown with 2016 and 2024 so you can see which way a county is moving, not only where it stands.
MIT Election Data and Science Lab · MIT county presidential returns
Average test score
How far above or below the national average children here score on tests, in grade levels. Minus one means about a year behind. It reflects everything in children's lives, not only their schools.
Stanford Education Data Archive · SEDA cs_mn_avg_ol
Highest and lowest
Where each measure is highest and lowest among the places reporting both (2023), with the other measure beside it. This is shown for every size of place where both are published. Metro-area values are added up from their counties. A measure that cannot be added up across counties, such as a middle value (median), has no metro figure. Counts are shown per 1,000 residents, since raw totals would only list the largest places. Cities and towns and ZIP codes are shown where the Census survey or the CDC publishes them; most other sources stop at the county. They are shown for places of 5,000 residents or more, and only where the survey’s margin of error is small enough for the figure to be usable. The CDC publishes its health estimates for cities in a version adjusted for age, so places with older or younger people can be compared fairly, but not for ZIP codes.
Counties
By republican share of the two-party vote, 2020
| Republican share of the two-party vote, 2020 | Average test score | |
|---|---|---|
| Highest | ||
| Borden County, TX | 96.1 | 0.408 |
| King County, TX | 95 | 0.226 |
| Garfield County, MT | 94.9 | 0.195 |
| Wallace County, KS | 94.6 | 0.26 |
| Glasscock County, TX | 94 | 0.237 |
| Lowest | ||
| Prince George's County, MD | 8.91 | -0.329 |
| Oglala Lakota County, SD | 9.5 | -1.12 |
| Baltimore city, MD | 10.9 | -0.611 |
| Petersburg city, VA | 11.3 | -0.54 |
| New York County, NY | 12.4 | 0.132 |
By average test score
| Republican share of the two-party vote, 2020 | Average test score | |
|---|---|---|
| Highest | ||
| Forsyth County, GA | 66.9 | 0.713 |
| Norfolk County, MA | 31.4 | 0.652 |
| Morris County, NJ | 47.8 | 0.627 |
| Williamson County, TN | 63.3 | 0.621 |
| Hamilton County, IN | 53.5 | 0.619 |
| Lowest | ||
| Todd County, SD | 21.3 | -1.21 |
| St. Helena Parish, LA | 44.8 | -1.16 |
| Sioux County, ND | 24.3 | -1.15 |
| Oglala Lakota County, SD | 9.5 | -1.12 |
| Allendale County, SC | 23.5 | -1.05 |
Metro areas
By republican share of the two-party vote, 2020
| Republican share of the two-party vote, 2020 | Average test score | |
|---|---|---|
| Highest | ||
| Gillette, WY | 89.8 | 0.145 |
| Pampa, TX | 89.7 | -0.211 |
| Cullman, AL | 89.2 | -0.0408 |
| Vernal, UT | 88.9 | -0.0541 |
| Borger, TX | 88.8 | -0.194 |
| Lowest | ||
| Santa Cruz-Watsonville, CA | 19.1 | -0.26 |
| San Francisco-Oakland-Fremont, CA | 19.6 | 0.011 |
| Vineyard Haven, MA | 21 | 0.583 |
| Boulder, CO | 21.1 | 0.45 |
| Taos, NM | 22.1 | -0.384 |
By average test score
| Republican share of the two-party vote, 2020 | Average test score | |
|---|---|---|
| Highest | ||
| Vineyard Haven, MA | 21 | 0.583 |
| North Platte, NE | 78.3 | 0.553 |
| Los Alamos, NM | 36.2 | 0.543 |
| Sheridan, WY | 74.5 | 0.536 |
| Lewisburg, PA | 62.3 | 0.521 |
| Lowest | ||
| Forrest City, AR | 47.4 | -0.774 |
| Shawano, WI | 64.7 | -0.756 |
| Selma, AL | 31.1 | -0.724 |
| Clarksdale, MS | 28.3 | -0.69 |
| Eufaula, AL-GA | 54 | -0.647 |
Counties furthest from the pattern
Compared with the straight line that best fits all 2,754 counties: the five with far more average test score than their republican share of the two-party vote, 2020 would suggest, and the five with far less.
| Republican share of the two-party vote, 2020 | Average test score | |
|---|---|---|
| Above the line | ||
| Norfolk County, MA | 31.4 | 0.652 |
| Forsyth County, GA | 66.9 | 0.713 |
| Dukes County, MA | 21 | 0.583 |
| Morris County, NJ | 47.8 | 0.627 |
| Falls Church city, VA | 17.3 | 0.562 |
| Below the line | ||
| Todd County, SD | 21.3 | -1.21 |
| St. Helena Parish, LA | 44.8 | -1.16 |
| Sioux County, ND | 24.3 | -1.15 |
| Oglala Lakota County, SD | 9.5 | -1.12 |
| Thurston County, NE | 51.3 | -1.02 |
Two series, one county
Both measures over time for a county you pick. The two charts are stacked, so they share only the years along the bottom. You can pick from the thirty largest counties reporting both. This panel covers 2010–2024, and a measure published only once shows as a single dot.
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Every version of the link
Each row measures the same link, from −1 to +1, in a different way. If the rows mostly agree, the link does not depend on one choice of method.
| Before adjusting for anything | +0.118 | 2,740 counties reporting both |
| After adjusting for density, income and education | +0.521 | the part of the link that is not just how urban, rich and educated a place is |
| Also adjusting for population size | +0.511 | size taken out as well as density |
| Also comparing only within each state | +0.562 | each county is compared only with others in its own state, so this is no longer a comparison between states |
| Giving bigger counties more weight | +0.587 | the adjusted link for the average resident rather than the average county. With this weighting, the data counts for about 267 equally weighted counties |
| Middle value inside single states | +0.066 | the link worked out inside each of 38 states with at least 20 counties reporting |
| Using ranks, after adjusting | +0.369 | uses each county’s rank, not its value, so a few extreme counties cannot create the link |
How much to believe it
Could it be chance?
The p-value is the chance of seeing a link this strong if there were really none. A value of 0.05 or less means the link is unlikely to be chance. Very small values are written in short form: 3.1e-16 means 0.00000000000000031, and the bigger the number after “e-”, the smaller the value. Treating every county as a separate case gives p = 9.8e-191. But counties in the same state tend to resemble each other, so the better figure allows for that: p = 1.2e-10. The site tested 20,910 pairs, and testing so many turns up some flukes. The q-value allows for that too. For this pair it is 1.1e-189.
Do nearby places look alike?
Moran’s I measures how much nearby places look alike: 0 means no map pattern, and higher means neighbours are more similar. For the part of each county that the adjustment leaves unexplained, it is +0.42 (p = 0.001). That unexplained part still clusters on the map. So some regional factor shared by both measures is not accounted for.
Did they change together?
Not measurable: at least one of these is published for too few of the years a change needs (2014–2019 or 2019–2023), or for too few counties in both.
Related pairs
- Housing insecurity and Average test score — -0.71
- Food insecurity and Average test score — -0.70
- Lack of reliable transportation and Average test score — -0.69
- Share White, not Hispanic and Average test score — +0.66
- Lacking social and emotional support and Average test score — -0.65
- Threat of utility shut-off and Average test score — -0.65
- Received food stamps and Average test score — -0.64
- Housing insecurity and Republican share of the two-party vote, 2020 — -0.62
Association only. Nothing here shows that either measure changes the other. This describes counties, not the people in them. Two measures going together across places does not mean the same people have both. How the US county data works · Explore Republican share of the two-party vote, 2020 and Average test score