Quarterly Journal of Political Science > Vol 8 > Issue 3

Unintentional Gerrymandering: Political Geography and Electoral Bias in Legislatures

Jowei Chen, Department of Political Science, University of Michigan, USA, jowei@umich.edu , Jonathan Rodden, Department of Political Science and Hoover Institution, Stanford University, USA, jrodden@stanford.edu
Suggested Citation
Jowei Chen and Jonathan Rodden (2013), "Unintentional Gerrymandering: Political Geography and Electoral Bias in Legislatures", Quarterly Journal of Political Science: Vol. 8: No. 3, pp 239-269. http://dx.doi.org/10.1561/100.00012033

Publication Date: 27 Jun 2013
© 2013 J. Chen and J. Rodden
Elections,  Representation,  Redistricting,  Partisan bias,  Simulations,  Vote-seat curve


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In this article:
1. Political Geography and the Roots of Electoral Bias in the United States 
2. Automated Districting and Electoral Bias 
3. Simulation Results 
4. A Closer Look at Political Geography 
5. Does Geography Constrain Partisan Gerrymandering? 
6. Simulation Results across U.S. States 
7. Discussion 


While conventional wisdom holds that partisan bias in U.S. legislative elections results from intentional partisan and racial gerrymandering, we demonstrate that substantial bias can also emerge from patterns of human geography. We show that in many states, Democrats are inefficiently concentrated in large cities and smaller industrial agglomerations such that they can expect to win fewer than 50% of the seats when they win 50% of the votes. To measure this "unintentional gerrymandering," we use automated districting simulations based on precinct-level 2000 presidential election results in several states. Our results illustrate a strong relationship between the geographic concentration of Democratic voters and electoral bias favoring Republicans.