Compactness: An R Package for Measuring Legislative District Compactness If You Only Know It When You See It

This software implements the methods in Kaufman, King, and Komisarchik, “How to Measure Legislative District Compactness If You Only Know It When You See It,” American Journal of Political Science. To deter gerrymandering, many U.S. state constitutions require legislative districts to be geographically “compact” (and a similar requirement holds explicitly or implicitly for numerous political jurisdictions around the world). Yet, the law offers few precise definitions other than “you know it when you see it,” which effectively implies a common understanding of the concept. In contrast, academics have shown that compactness has multiple dimensions and have generated many conflicting measures. The authors hypothesize that both are correct—that compactness is complex and multidimensional, but a single common understanding exists across people. They develop a survey to elicit this understanding, with high reliability (in data where the standard paired comparisons approach fails). They then create a statistical model that predicts, with high accuracy, solely from the geometric features of the district, compactness evaluations by judges and public officials responsible for redistricting, among many others. The project also offers compactness data from a validated measure for many state legislative and congressional districts, and software to compute this measure from any district.