The Impact of Political Geography on Wisconsin Redistricting: An Analysis of Wisconsin's Act 43 Assembly Districting Plan

Abstract This article illustrates how the relationship between political geography and the electoral bias of a districting plan, as measured by the efficiency gap, can be analyzed in a statistically rigorous manner using computer simulations of the legislative redistricting process. By generating a large number of different districting plans designed to optimize on traditional redistricting criteria, the computer simulation process demonstrates the range of districting plans that would likely emerge from a neutral, non-gerrymandered process. Courts and litigants can then draw inferences by comparing the efficiency gap of an enacted districting plan against this range of simulated plans. I use this method to illustrate how Wisconsin's Act 43 created an Assembly districting plan with an extreme, Republican-favoring efficiency gap that would not have been possible under a map-drawing process that prioritizes traditional redistricting criteria.