MODELING THE EFFECT OF MANDATORY DISTRICT COMPACTNESS ON PARTISAN GERRYMANDERS

Geographic compactness standards have been offered as neutral and effe ctive standards constraining redistricting. In this paper, we test thi s allegation. Redistricting is treated as a combinatoric optimization problem that is constrained by compactness rules. Computer models are used to analyze the results of applying compactness standards when pol itical groups are geographically concentrated. Several population mode ls are used to generate populations of voters, and arbitrary plans are created with combinatoric optimization algorithms. We find that compa ctness standards can be used to limit gerrymandering, but only if such standards require severe compactness. Compactness standards are not p olitically neutral-a geographically concentrated minority party will b e affected by com pactness standards much differently than a party sup ported by a geographically diffuse population. The particular effects of compactness standards depend on the institutional mechanism that cr eates districts. (C) 1998 Elsevier Science Ltd. All rights reserved.