Causes and Extent of Increasing Partisan Segregation in the U.S. – Evidence from Migration Patterns of 212 Million Voters

Using data on the residential location and migration for every voter in U.S. states recording partisan registration between 2008–2020, we find that residential segregation between Democrats and Republicans has increased year over year at all geographic levels, from neighborhoods to Congressional Districts. Individual demographic information reveals that segregation increases for voters of most demographic backgrounds, but that Democratic and Republican trending places have starkly different demographic profiles, thus contributing to the growing confluence of demographics, partisanship, and geography in the United States. We further decompose the change in segregation into different sources. Increases in segregation have not been driven primarily by migration but rather by generational change, as young voters enter the electorate, causing some places to become more homogeneously Democratic, and by existing voters leaving the Democratic party and causing other places to become more Republican.