They tracked migration flows through voter files from 2004, 2006, and 2008 in seven states (New Jersey, Maryland, Delaware, Pennsylvania, California, Oregon, and Nevada). While these data do not represent all migrants, they do represent those who are more politically interested and active, and who are most likely to influence the political landscape.
Cho, Gimpel and Hui found some interesting patterns:
- Democrats seem to prefer densely populated areas more than Republicans perhaps, the researchers surmise, because large cities tend to be Democratic ("partisan attraction").
- The tendency of Republicans to sort is stronger than their tendency to mix. Democrats, on the other hand, mix more than they sort.
- "Factors such as racial composition, income, population density, and age all display a consistent relationship with destination choices. There is, moreover, a strong tendency for individuals to move toward neighborhoods that are more white, less black, less dense, and with higher incomes." This could be a reflection the fact that relocation is often associated with upward mobility. But the authors note that migration determinants (income, racial composition, etc.) might be correlated with partisanship: for instance, "if Republicans are wealthier and prefer newer housing and expansive acreages, then the geographic preferences of Republicans and Democrats might be artifacts of the income distribution and the expression of the purchasing power of the rival partisan groups."
- Partisanship remains a significant factor, even after other neighborhood characteristics are taken into account: "Specifically, Republican migrants show a preference for moving to areas that are even more Republican, and this tendency increases monotonically as the distance of the move increases. Democrats display a similar preference for their own, though the tendency is not as strong as it is for Republicans.”
The researchers concluded that “[w]hether the role of partisanship is central or ancillary, if it is part of the decision process, it has the potential to recast the political landscape of the United States.” As others have argued, as the geographic clustering of the like-minded increases, we become more likely to fall victim to narrowness of viewpoint, extremism, and ideological intensity: "The result, some bewail, is a polity wherein citizens are deeply divided, parties are polarized, and political discourse is stifled."
Cho, Gimpel and Hui's findings are consistent with the results of a recent Pew Research Center study on political polarization that found that Republicans and Democrats are more ideologically divided than in the past, and that differences between the right and left go beyond politics: "Three-quarters of consistent conservatives say they would opt to live in a community where 'the houses are larger and farther apart, but schools, stores and restaurants are several miles away,' while 77% of consistent liberals prefer smaller houses closer to amenities. Nearly four times as many liberals as conservatives say it is important that their community has racial and ethnic diversity; about three times as many conservatives as liberals say it is important that many in the community share their religious faith."
For more data and an in-depth look at political polarization in the U.S., including interactive charts, check out the Pew Research Center report at http://www.people-press.org/2014/06/12/political-polarization-in-the-american-public/