Historical Data

PlanScore presents estimates of how severe state's gerrymander is by measuring today's maps against historical data.

Learn more about PlanScore's data sources.


At the congressional level, we relied on datasets assembled by Gary Jacobson and Gary King.

At the state legislative level, Carl Klarner of Klarner Politics provided us with all of the relevant data.

The Impact of Partisan Gerrymandering on Political Parties, Nicholas Stephanopoulos and Christopher Warshaw’s February 2020 article for Legislative Studies Quarterly.

Assessing the Current Wisconsin State Legislative Districting Plan, Simon Jackman’s 2015 expert witness report in Gill v. Whitford, analyzing state legislative plans.

Assessing the Current North Carolina Congressional Districting Plan, Simon Jackman’s 2017 expert witness report in LWVNC v. Rucho, analyzing congressional plans.

The Experts

Simon Jackman, Eric McGhee, and Nicholas Stephanopoulos compiled these estimates in their academic and litigation-related work.