I got ahold of the county-level election returns from 2008 (as of a few days ago, so lots of precincts missing, but that’s what I have to go with for now) and crosstabbed it with county income, dividing the counties into poorest, middle, and upper third, with cutpoints set so that approximately one-third of the U.S. population is in each category.
What happened in each lower, middle-income, and rich America?
Obama did better than Kerry in all three graphs, but he did most uniformly better in the rich counties. (In this and subsequent graphs, the area of the circle is proportional to the number of voters in that county in 2004. It turns out that Obama did the worst, compared to Kerry, in low-population poor counties, so the graphs actually look a bit different if you plot all counties with equal-sized circles.)
These patterns are new to 2008. Checking the corresponding plots from 2000/2004 and 1996/2000, we don’t see much of anything different comparing poor, middle-income, and rich counties.
The next step is to break things up by region of the country. Here’s what we see:
In the midwest and west, Obama outperformed Kerry in all sorts of counties. In the northeast, Obama did just a bit better than Kerry (who had that northeastern home-state advantage). In the south, Obama did almost uniformly better in rich counties, also did well in middle-income counties (although less so in Republican-leaning areas), and basically showed no improvement from Kerry in poor counties.
So, region and income are both part of the story here. As we already know from those maps of vote swing by county. These scatterplots are another way to look at it.
What happened in the two previous elections?
Let’s take a look at the swings from 2000 to 2004:
Nothing much here. But what about the 1996/2000 swing?
This is interesting. Gore held performed about as well as Clinton in most of the middle-income and rich counties but he got nuked in poor counties in all regions of the country. Consistent with the David Brooks story about growing divisions between Red and Blue America.
P.S. Thanks for Cosma Shalizi, Yair Ghitza, and Boris Shor for grabbing and putting together the data.
P.P.S. Recall that the 2008 data are incomplete. Out of 3114 rows in the data, 23 rows have < 50%, 49 rows have 50-75%, 68 rows have 75-90%, 117 have 90-99%, and 2857 have 100% reporting. So at some point we'll need to redo these graphs. P.P.P.S. Yes, I know that income isn't all. Feel free to take these data and run whatever regressions you want, including %black and anything else you're interested in. That said, I think the above plots are interesting--especially considering that the patterns in 1996/2000 and 2000/2004 were different.