An interesting use of data: Obama votes and cotton production circa 1860

This semester I am teaching the second semester of "core" microeconomic theory to a crop of 25 PhD students. The class is a notorious tough slog--a lot of material, a lot of math, and way more abstraction than students see in undergraduate training. This is stuff all Ph.D.s need to know. But getting so much of it over a short period of time can sometimes stunt natural creative tendencies.

So to help keep students' minds open, I'm adopting a set of assignments that George Akerlof gave when he taught macroeconomics at Berkeley. The first assignment is to find an interesting use of data (preferably from one of the best economics journals) and summarize it in 400 words, plus maybe one figure or one table. We will then meet in small groups and discuss them.

In class I gave a couple examples from the academic literature that interested me. Here is one I just stumbled upon on the internet. The black dots indicate cotton production circa 1860. The colored counties show the 2008 Presidential election results, more blue is more votes for Obama.



The map sure is striking. A little tickle in the back of my mind is thinking of all those papers with demographic variables on the right-hand-side of regressions and thinking they really are not so exogenous. (Well, actually, I've always thought that.) A form of Tiebout sorting? Strong historisis or path-dependency? Some of both, probably. I'm especially curious about the exception in southern Tennessee/Alabama border. What do you think?