[EL] new study of density/compactness and district bias/responsiveness

[Kieran Williams]

http://www.bepress.com/spp/vol2/iss1/3/

Using a Density-Variation/Compactness Measure to Evaluate Redistricting Plans 
for Partisan Bias and Electoral Responsiveness
Thomas R. Belin, University of California, Los Angeles
Heidi J. Fischer, University of California, Los Angeles
Corwin M. Zigler, Harvard University

Abstract
The clear association between population density and partisan preference in 
elections suggests that redistricting plans would be better aligned with 
principles of partisan fairness if there were a deliberate effort to balance 
population density across legislative districts. To balance population density 
without sacrificing geometric compactness, we define a 
density-variation/compactness (DVC) measure that can serve as a one-number 
summary of a proposed redistricting plan. After analyzing voter registration 
data from California to guide the choice of a specific DVC measure, we evaluate 
its performance in both actual and hypothetical redistricting plans using 
election data from Texas during the past decade. Using a well-established 
political-science model of the relationship between legislative representation 
and the proportion of votes received, higher DVC scores corresponded to 
estimates of partisan bias with smaller magnitude across a range of 
redistricting scenarios; meanwhile, contrary to expectations that reduced 
partisan bias would be accompanied by reduced electoral responsiveness, there 
was no discernible pattern between DVC scores and estimates of electoral 
responsiveness. Although there are apt to be multiple considerations in choosing 

a redistricting plan, we discuss how the use of DVC measures could provide a 
check on attempts to introduce partisan bias into the redistricting process.
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