We clarify the theoretical foundations of partisan fairness standards for district-based democratic electoral systems, including essential assumptions and definitions not previously recognized, formalized, or in some cases even discussed. We also offer extensive empirical evidence for assumptions with observable implications. We cover partisan symmetry, the most commonly accepted fairness standard, and other perspectives. Throughout, we follow a fundamental principle of statistical inference too often ignored in this literature—defining the quantity of interest separately so its measures can be proven wrong, evaluated, and improved. This enables us to prove which of the many newly proposed fairness measures are statistically appropriate and which are biased, limited, or not measures of the theoretical quantity they seek to estimate at all. Because real-world redistricting and gerrymandering involve complicated politics with numerous participants and conflicting goals, measures biased for partisan fairness sometimes still provide useful descriptions of other aspects of electoral systems.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/86DAD2FE5F86E72D75A9704DFD7D192E/S000305541900056Xa.pdf/div-class-title-theoretical-foundations-and-empirical-evaluations-of-partisan-fairness-in-district-based-democracies-div.pdf

Theoretical Foundations and Empirical Evaluations of Partisan Fairness in District-Based Democracies

Since the United States Supreme Court’s Davis v. Bandemer ruling in 1986, partisan gerrymandering for statewide electoral advantage has been held to be justiciable. The existing Supreme Court standard, culminating in Vieth v. Jubelirer and LULAC v. Perry, holds that a test for gerrymandering should demonstrate both intents and effects, and that partisan gerrymandering may be recognizable by its asymmetry: for a given distribution of popular votes, if the parties switch places in popular vote, the numbers of seats will change in an unequal fashion. However, the asymmetry standard is only a broad statement of principle, and no analytical method for assessing asymmetry has yet been held by the Supreme Court to be manageable. This Article proposes three statistical tests to reliably assess asymmetry in state-level districting schemes: (a) an unrepresentative distortion in the number of seats won based on expectations from nationwide district characteristics; (b) a discrepancy in winning vote margins between the two parties; and (c) the construction of reliable wins for the party in charge of redistricting, as measured by either the difference between mean and median vote share, or an unusually even distribution of votes across districts. The first test relies on computer simulation to estimate appropriate levels of representation for a given level of popular vote, and provides a way to measure the effects of a gerrymander. The second and third tests, which evaluate intent, rely on well-established statistical principles, and can be carried out using a hand calculator without examination of maps or redistricting procedures. I apply these standards to a variety of districting schemes, starting from the original “Gerry-manderˮ of 1812 up to modern cases. In post-2010 Congressional elections, partisan gerrymandering in a handful of states generated effects that are larger than the total nationwide effect of population clustering. By applying these standards in two recent cases, I show that Arizona legislative districts (Harris v. Arizona Independent Redistricting Commission) fail to qualify as a partisan gerrymander, but Maryland’s Congressional districts (Shapiro v. McManus) do. I propose that an intents-and-effects standard based on these tests is robust enough to mitigate the need to demonstrate predominant partisan intent. The three statistical standards offered here add to the judge’s toolkit for rapidly and rigorously identifying the effects of redistricting.

https://papers.ssrn.com/sol3/Delivery.cfm/SSRN_ID2760107_code2459280.pdf?abstractid=2671607&mirid=1&type=2

Three Tests for Practical Evaluation of Partisan Gerrymandering

The relationship between votes and seats in the legislature lies at the heart of democratic governance. However, there has been little previous work on the downstream effects of partisan gerrymandering on the health of political parties. In this study, we conduct a comprehensive examination of the impact of partisan advantage in the districting process on an array of downstream outcomes. We find that districting bias impedes numerous party functions at both the congressional and state house levels. Candidates are less likely to contest districts when their party is disadvantaged by a districting plan. Candidates that do choose to run are more likely to have weak resumes. Donors are less willing to contribute money. And ordinary voters are less apt to support the targeted party. These results suggest that gerrymandering has long-term effects on the health of the democratic process beyond simply costing or gaining parties seats in the legislature.

The Impact of Partisan Gerrymandering on Political Parties

The recent wave of attention to partisan gerrymandering has come with a push to refine or replace the laws that govern political redistricting around the country. A common element in several states...

A Computational Approach to Measuring Vote Elasticity and Competitiveness

Congressional redistricting plans for Pennsylvania, with an emphasis on the newly enacted 2018 plan, have been evaluated for fairness and responsiveness to voters. This and other submitted...

What Criteria Should Be Used for Redistricting Reform

Courts have found it difficult to evaluate whether redistricting authorities have engaged in constitutionally impermissible partisan gerrymandering The knotty problem is that no proposed standard has found acceptance as a convincing means for identifying whether a districting plan is a partisan gerrymander with knowable unconstitutional effects We review five proposed standards for curbing gerrymandering We take as our perspective how easily manageable and effective each would be to apply at the time a redistricting authority decides where to draw the lines or, post hoc, when a court is asked to decide whether an unconstitutional gerrymander has been enacted We conclude that, among the five proposals, an equal vote weight standard offers the best prospects for identifying the form of unconstitutional gerrymanders that all but ensure one party is relegated to perpetual minority status

Considering the Prospects for Establishing a Packing Gerrymandering Standard

We explain why Eric McGhee's criticisms of our effort to establish a standard for detecting packing gerrymanders sometimes misapprehends and other times misunderstands the proper evaluatio...

Authors' Response to elj.2017.0461–Values and Validations: Proper Criteria for Comparing Standards for Packing Gerrymanders

In light of the Supreme Court's ruling in Gill v. Whitford (2018), we propose two paths forward for establishing manageable standards to identify partisan gerrymanders. One is aimed most p...

J DonahueShawn

Papers

Considering the Prospects for Establishing a Packing Gerrymandering Standard

Authors' Response to elj.2017.0461–Values and Validations: Proper Criteria for Comparing Standards for Packing Gerrymanders

Making a Case for Two Paths Forward in Light of Gill v. Whitford