How is it the Economy, Stupid?

Andrew Gelman summarizes some current research by Larry Bartels on income, economic growth and voting.

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Larry Bartels spoke in our seminar the other day and talked about this paper on Democrats, Republicans, and the economy. It started with this graph, which showed that incomes have grown faster under Democratic presidents, especially on the low end of the scale:

He looked at it in a number of ways, and the evidence seemed convincing that, at least in the short term, the Democrats were better than Republicans for the economy. This is consistent with Democrats’ general policies of lowering unemployment, as compared to Republicans lowering inflation, and, by comparing first-term to second-term presidents, he found that the result couldn’t simply be explained as a rebound or alternation pattern.

But then, he asked, why have the Republicans won so many elections? Why aren’t the Democrats consistently dominating? Non-economic issues are part of the story, of course, but lots of evidence shows the economy to be a key concern for voters, so it’s still hard to see how, with a pattern such as shown above, the Republicans could keep winning.