Unintentional Gerrymandering: Political Geography and Electoral Bias in Legislatures

Here’s some very interesting research on gerrymandering, especially relevant for pundits and journalists who have been citing gerrymandering as one of the main causes of today’s gridlock and government shutdown. Roughly speaking, Jowei Chen and Jonathan Rodden show that having a computer randomly draw up contiguous districts results in pro-republican allocations (due to the residential choices of republicans and democrats).

We show that in many urbanized states, Democrats are highly clustered in dense central city areas, while Republicans are scattered more evenly through the suburban, exurban, and rural periphery. We illuminate this pattern with an in depth case study of Florida and demonstrate that it holds up in many other states. Precincts in which Democrats typically form majorities tend to be more homogeneous and extreme than Republican-leaning precincts. When these Democratic precincts are combined with neighboring precincts to form legislative districts, the nearest neighbors of extremely Democratic precincts are more likely to be similarly extreme than is true for Republican precincts. As a result, when districting plans are completed, Democrats tend to be inefficiently packed in homogeneous districts.

This observation raises some vexing empirical questions: To what extent is observed pro-Republican electoral bias a function of human geography rather than intentional gerrymandering? To what extent might pro-Republican bias persist in the absence of partisan and racial gerrymandering?

The main contribution of this paper is to answer these questions by generating a large number of hypothetical alternative districting plans that are blind as to party and race, relying only on criteria of geographic contiguity and compactness. We achieve this through a series of automated districting simulations. The simulation results provide a useful benchmark against which to contrast observed districting plans. We show that in general, pro-Republican partisan bias is quite persistent in the absence of intentional gerrymandering. Moreover, consistent with our argument about human geography, we demonstrate that the highest levels of electoral bias against Democrats occur in states where Democratic voters are most concentrated in urban areas.

HT: Kyle Dropp


About ozidar

I'm an Assistant Professor of Economics at the University of Chicago Booth School of Business and a Faculty Research Fellow at National Bureau of Economic Research. You can follow me on twitter @omzidar. http://faculty.chicagobooth.edu/owen.zidar/index.html
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