When I describe an increasing correlation between density and Democratic voting that took off after the 1980s, this is the rise not only of globalization and the knowledge economy in that period, but also the rise of politics related to religion, gender, and the social transformations that came about in the ‘60s and ‘70s and then were politicized in the ‘80s. Before the 1980s, it was not clear if one was a social conservative and one was anti-abortion whether one should be a Democrat or a Republican. That became much more clear in the 1980s when the parties took very sharply different positions on those issues. One’s preferences on those issues are also highly correlated with population density.
Once we add this additional set of issues, it all starts to bunch together. The parties become increasingly separated in their geographies. The Democrats go from not only being a party of urban workers, but also being a party of urban social progressives, which leads to further sorting of individuals into the parties. Knowing someone’s preferences and whether they call themselves a liberal or a conservative becomes much more predictive of whether they vote for Democrats or Republicans.
There's a real geographic story to that as well. These people who are sorting into the parties in this period are geographically located in ways that are quite clear. It all leads to an increase in this correlation between population density and Democratic voting. All that comes together and we end up with these two parties that offer a set of policies that might not even make that much sense anymore to refer to them as left and right. It makes more sense to refer to them as urban and rural because of the way they’re packaged together.
JONATHAN RODDEN is a professor in the Political Science Department at Stanford and a Senior Fellow at the Hoover Institution. Jonathan Rodden's Edge Bio Page