With the launch of its new Partisan Advantage Tracker, the Institute for Public Policy and Social Research has provided an important and accessible tool for measuring the extent to which district maps for U.S. House elections favor one party over another. The Tracker monitors the partisan advantage of each state’s map by comparing the number of seats a party will win (determined as an average using recent election data) to the number of seats a party should win according to each of four notions of fairness. By measuring a map’s unfairness in terms of excess seats, the Tracker assesses maps in a natural and fundamental way that is both useful to those involved in the districting process and understandable to a general audience.
Results for the partisan advantage in each state relative to each of the four fairness standards are arranged in a simple, color-coded table that may be sorted according to each metric. This presentation allows users to easily ascertain the magnitude and beneficiary of the partisan advantage in every state along with the nationwide total advantage for each measure. The tracker also provides customizable heat maps of the U.S. that allow users to instantly visualize the tabulated results for their preferred measure or for an overall average of the four.
For those whose interest extends beyond the results, clear and concise discussions of the methodology, the data used, and the four notions of fairness are included as expandable sections. Users may also find further information on the theoretical underpinnings of the four fairness standards in a linked PDF file. This document provides a well-written overview that is suitable for a general audience and includes references to the more technical source material. Links to all data sources as well as several other interesting redistricting resources are provided at the bottom of the Tracker’s homepage.
With its combination of clear exposition, user-friendly presentation, and accessibility, the Partisan Advantage Tracker should become a go-to resource for those seeking to understand both the state-by-state and nationwide partisan advantage inherent in current district maps.
Jeff Barton received his Ph.D. in mathematics from The University of Texas at Austin and is currently a professor of mathematics at Birmingham-Southern College. He has an interest in redistricting, and his recent work includes the Mathematical Social Sciences article “Fairness in Plurality Systems with Implications for Detecting Partisan Gerrymandering.” He is also the author of Models for Life, an introductory mathematical modeling textbook published by John Wiley & Sons. For more information, including how to contact him, please click here.
IPPSR's new Partisan Advantage Tracker stems from the Institute's landmark redistricting analysis of Michigan's 2021 state House of Representatives, state Senate and U.S. Congressional maps. This work is the research of Michigan State University Economist Dr. Jon X. Eguia, Ph.D., and IPPSR Director Dr. Matt Grossmann, Ph.D., professor of political scientist. It was conducted through a grant from The Joyce Foundation and in conjunction with the University of Michigan's Center For Local, State and Urban Policy (CLOSUP) in the Ford School of Public Policy. See the analysis and a special webinar.