A Component Framework for Assessing Partisan Fairness in District Maps

Abstract

By removing different sources of bias from the redistricting process, each of three recent methods -- the jurisdictional method, computer simulations, and the quadratic rule -- offer a different perspective on partisan fairness. We combine these approaches to resolve the overall partisan advantage of district maps into three distinct sources: a state's natural political geography, a state's map-drawing rules, and partisan gerrymandering. This component analysis allows us to distinguish unfair maps from those that are just unusually partisan, and it has implications for potential remedies for any unfairness. Finally, we analyze maps according to who controls the redistricting process in a way that clarifies and reinforces previous work showing that independence in the process is an important contributor to fairness.

Keywords: gerrymandering, partisan advantage, quadratic rule, redistricting