The Measure of a Metric: The Debate Over Quantifying Partisan Gerrymandering

Abstract

Over the last few years, there has been an unprecedented outpouring of scholarship on partisan gerrymandering. Much of this work has sought either to introduce new measures of gerrymandering or to analyze a metric — the efficiency gap — that we previously developed. In this Article, we reframe this debate by presenting a series of criteria that can be used to evaluate gerrymandering metrics: (1) consistency with the efficiency principle; (2) distinctness from other electoral values; (3) breadth of scope; and (4) correspondence with electoral history. We then apply these criteria to both the efficiency gap and other measures. The efficiency gap complies with the criteria under all circumstances. Other metrics, in contrast, often violate the efficiency principle and cannot be used in certain electoral settings.

Keywords: Election law; redistricting; partisan gerrymandering