Three Practical Tests for Gerrymandering: Application to Maryland and Wisconsin

Abstract Partisan gerrymandering arises when many single-district gerrymanders are combined to obtain an overall advantage. The Supreme Court has held that partisan gerrymandering is recognizable by its asymmetry: for a given distribution of popular votes, if the parties switch places in popular vote, the numbers of seats would change in an unequal fashion. However, the asymmetry standard is only a broad statement of principle, and no analytical method for assessing asymmetry has yet been held to be manageable. Recently I proposed (68 Stanford Law Review 1263) three statistical tests to reliably assess asymmetry in state-level districting schemes: (a) a discrepancy in winning vote margins between the two parties' seats; (b) undue reliable wins for the party in charge of redistricting, as measured by the mean-median difference in vote share, or by an unusually even distribution of votes across districts; and (c) unrepresentative distortion in the number of seats won based on expectations from nationwide di...