Americans Are Geographically Segregated By Politics

The conclusion isn't new, but it replicates past work and points to a divide even stronger than previously indicated, with a massive and extremely detailed data set.

Nationwide percentiles of partisan exposure by party and race. Courtesy of Nature Human Behaviour.

New research on political behavior finds that most Democratic and Republican voters live in partisan bubbles, with little daily exposure to those who belong to the other party. For instance the typical Democrat has “almost zero interactions” with Republicans in their neighborhood, according to an article by Harvard doctoral student Jacob R. Brown and government Professor Ryan D. Enos published March 8 in the journal Nature Human Behaviour. . . .

Using geolocation data and the exact addresses of all 180 million registered voters in the U.S. as of June 2018, the two were able to precisely map, for the first time, where Democrats and Republicans live in relation to each other in every town, city, and state in the U.S. Then, rather than rely on the usual precinct or data aggregations, they used weighted measures and recorded the distance between voters to show how people are divided by geography and partisanship across the country.

Democrats in large, densely populated cities like New York are the most politically isolated, with 10 percent of them encountering a Republican only one out of 10 times in their neighborhood. Republicans in rural areas are similarly segregated.

Overall, most Democrats and Republicans live in levels of partisan segregation that exceed what scholars of racial segregation consider highly segregated, the study found. . . . 

Their analysis of U.S. Census tract data showed that 98 to 99 percent of Americans live in areas segregated by partisanship. Loving County, Texas, a county of about 200 people along the New Mexico border, is the only tract in the entire U.S. where Democrats and Republicans mix freely, the researchers found.

This social splitting is not the result of an urban/rural divide, where cities attract more Democrats, and Republicans typically favor the country life, Brown and Enos say. Whether in small to mid-size cities, the suburbs or ex-urbs in between, the data showed that Republicans stick close to other Republicans, and Democrats stick close to other Democrats.

“Even within a neighborhood, Democrats and Republicans are separating from each other a little bit,” said Enos. . . .

White Democrats who do not identify as Hispanic had similar levels of exposure to members of the other political party as white Republicans, levels that were greater than Democrats from other racial and ethnic groups, who are the most isolated."

From here.

The article and its abstract are as follows:

Segregation across social groups is an enduring feature of nearly all human societies and is associated with numerous social maladies. In many countries, reports of growing geographic political polarization raise concerns about the stability of democratic governance. 

Here, using advances in spatial data computation, we measure individual partisan segregation by calculating the local residential segregation of every registered voter in the United States, creating a spatially weighted measure for more than 180 million individuals. 

With these data, we present evidence of extensive partisan segregation in the country. A large proportion of voters live with virtually no exposure to voters from the other party in their residential environment. Such high levels of partisan isolation can be found across a range of places and densities and are distinct from racial and ethnic segregation. Moreover, Democrats and Republicans living in the same city, or even the same neighbourhood, are segregated by party.

Brown, J.R., Enos, R.D., "The measurement of partisan sorting for 180 million voters." Nat Hum Behav (March 8, 2021). https://doi.org/10.1038/s41562-021-01066-z