Unfair Partisan Gerrymanders in Politics and Law: A Diagnostic Applied to Six Cases

Abstract We propose standards for detecting partisan gerrymandering as a finding of fact and for determining whether the factual finding is legally significant. The standard is grounded in the U.S. constitutional principle of equal voting rights and is easily manageable inasmuch as its prime analytical feature requires comparing a party's district median vote percentage to its district mean vote percentage. Equally important, the median-mean comparison serves as an effective indicator of whether gerrymandering is the cause of the inequitable treatment. We apply the standard to six alleged cases of gerrymandering of congressional districts and find three cases are not gerrymanders, three are gerrymanders, and one of the three gerrymanders crosses the threshold to legal significance.