Via Matt Yglesias (and Brendan Nyhan) some very interesting graphs on political party "polarization." Yglesias commenter Petey observes that there is significant overlap, according to these graphs, of "polarization" and high levels of foreign-born residents/high levels of income inequality; the greater the percentage of foreign-born residents/the greater the share of national assets that the top 1% owns, the greater the polarization. It's important to remember that correlation need not be causation, but they are some interesting graphs (depending, perhaps, on how you want to think of "party polarization"). And, certainly, those could not be the only causes of polarization (if they are causes at all).