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.
From the article:
The high levels of partisan segregation can probably be explained by two broad and different, but not mutually exclusive, mechanisms that may provide fruitful areas for future research. First, previous research has shown that the correlation between residential density and partisanship has long historical roots related to Democrats and Republicans sorting into different types of housing, often as a function of occupation and income, producing stable geographic patterns of partisanship even across generations41. This points to partisan segregation arising largely from the immobility of voters. A second mechanism, consistent with the sorting that is found even within neighbourhoods and with the partisan sorting that is in addition to racial sorting, is the influence of micro-level behaviours on these large-scale patterns. While the best available evidence shows that most voters consider the partisan composition of an area to be low on their list of priorities when choosing neighbourhoods52, it is still possible that partisan differences in income and lifestyle preferences, such as transportation and type of housing, may drive some voters to select different cities, neighbourhoods and, in some cases, streets or houses within neighbourhoods, even if partisanship is not an explicit criterion for selection. As partisanship becomes more correlated with lifestyle differences, such sorting may be further exacerbated.