Evidence in Voting Rights Act Litigation: Producing Accurate Estimates of Racial Voting Patterns

Abstract

Voting Rights Act litigation, even in the wake of Shelby County v. Holder, requires estimates of racial bloc voting, or the extent to which members of different racial groups vote differently. Although there are a variety of methods to make these estimates, direct evaluation and comparison of these methods is lacking. I examine these alternate methods in the way that they might be used in litigation using a large dataset of partisanship and racial information at the precinct level in five states. Additionally, I extend the application of these methods to estimation of racial group preferences in locations with more than one racial minority and assess the contextual determinants of larger and smaller errors in ecological regression estimates. I conclude that the ecological inference method developed by King (1997), which incorporates the deterministic precinct-level bounds on the quantities of interest and is easily implemented using open-source software, provides the best estimates for precinct-specific racial polarization using a binary racial split. When accounting for more than two racial groups, however, a similar but modified Multinomial-Dirichlet Bayesian model performs marginally better.