Awhile ago I posted some maps based on the Pew pre-election polls to estimate how Obama and McCain did among different income groups, for all voters and for non-Hispanic whites alone. The next day the blogger and political activist Kos posted some criticisms. I disagree with one of Kos's suggestions--he wanted me to rely on exit polls, but I don't actually see them as more reliable than the Pew pre-election polls--but he pointed out some serious problems with my maps. I realized that some fixes were in order. Most importantly:
- My maps would be improved by replacing solid red and blue with continuous shading to distinguish between landslides and narrow margins.
- I needed a more flexible model that would allow the nonlinear pattern of voting and income to vary by state. (In the previous model, I fit a nonlinear pattern (by including a separate logistic regression coefficient for each of the five income categories) but allowed the states to vary only with intercepts and slopes. In the new model, we're letting all five coefficients vary by state.)
During the past couple of months, I've been working on this when I've had a spare hour or two, and now I think we have something reasonable to share. Here it is:
States colored deep red and deep blue indicate clear McCain and Obama wins; pink and light blue represent wins by narrower margins, with a continuous range of shades going to pure white for states estimated at exactly 50/50.
I know that the 538 audience is more interested in results than in technical details, so I've put the detailed state-by-state discussion at my statistical modeling blog (along with a graph showing data and fitted model for each state).
All this work is joint with Yair Ghitza.
P.S. We did not include Alaska and Hawaii on the maps because they were not included in the Pew Research surveys that we analyzed.