Campaigns and elections

Don’t blame gerrymandering

Andrew Gelman Feb 18 '09

Matthew Yglesias quotes Richard Cohen presenting a common misconception:

Reality is real. No amount of lofty rhetoric is going to change the way members of Congress are elected. Most of them come from exquisitely gerrymandered districts created by computers that could, if good taste allowed, part the marital bed, separating husband from wife if they were of different political parties. This system created districts that are frequently reliably liberal or conservative. The computer has deleted the middle.

I can’t disagree with Cohen’s first sentence above, but I part company with him after that. When Gary and I looked at the data, we found that redistricting (“gerrymandering”) was not associated with a decline in competitiveness of elections in Congress or state legislatures. Legislative elections have been gradually becoming less competitive, but they are typically more competitive after redistricting.

I’m not saying that “gerrymandering” is a good thing–I’d prefer bipartisan redistricting or some sort of impartial system–but the data do not support the idea that redistricting is some sort of incumbent protection plan or exacerbator of partisan division.

In addition, political scientists have frequently noted that Democrats and Republicans have become increasingly polarized in the Senate as well as in the House, even though Senate seats are not redistricted.

P.S. I’m not saying that gerrymandering is always benign; there are certainly some places where it has been used to make districts with unnecessarily high partisan concentrations. But, in aggregate, that’s not what has happened, at least according to our research. (Also, our above-cited research is over 15 years old, and it’s possible that things have changed since then, with the advent of computer-based redistricting. But I haven’t seen any evidence for such a claim. I’d certainly love to see someone replicate our 1991 and 1994 articles to include the data up to the present.)

P.P.S. Update with more recent research (by Abramowitz, Alexander, and Gunning) here.