Gerrymandering and the Extent of Democracy in America (2018-2019)

Gerrymandering has been present in our democracy since the early 19th century. Courts have struck down district maps that clearly disadvantage racial minorities, but they have often declined to intervene in cases where maps intentionally favor a political party, in part because they lack a credible way of assessing such claims.

In 2012, Math professor Jonathan Mattingly watched this dynamic play out in North Carolina, where Republicans won nine of the 13 seats for the U.S. House of Representatives, even though Democrats received 51% of the votes. Interested in exploring gerrymandering, Mattingly partnered with an undergraduate on a summer research project. Using votes cast in the 2012 election to evaluate hundreds of alternative district maps, they were unable to find a single map that led to the same outcome.

A series of Data+ summer teams in 2015 and 2018 extended the analysis to other states, and several external partners joined the effort. In 2018-2019, this project team compared districting plans across states, analyzed the effectiveness of statistical tests currently used to detect gerrymandering and finished analyzing the extent of gerrymandering in the North Carolina General Assembly. Team members also worked with four local high school students to develop two new algorithms that generate representative collections of redistricting plans, and study how counties must be split to adhere to “one person, one vote” redistricting criteria.

The team saw this research travel all the way to the U.S. Supreme Court. Oral arguments for Common Cause v. Rucho occurred on March 26, 2019; the evidence for this case rested heavily on the expert testimony of Mattingly and the accompanying research, with significant contributions from undergraduates. In addition, the team helped conduct research investigating gerrymandering in the North Carolina legislature, which went into an expert report for Common Cause v. Lewis.

Timing

Fall 2018 – Spring 2019

Team Outputs

Impact of Gerrymandering in America (poster by Gillian Samios, Isaac Nicchitta, Mitra Kiciman, Nima Mohammadi, Rayan Tofique, Yashas Manjunatha, presented at Bass Connections Showcase, Duke University, April 17, 2019)

Gerrymandering in the North Carolina State Legislature (poster by Rahul Ramesh, Jacob Rubin, Haley Sink, Sam Eure, presented at Bass Connections Showcase, Duke University, April 17, 2019)

Detecting a Gerrymander: Sampling the Space of Possible NC Congressional Maps (poster by Luke Farrell, Jacob Shulman, Tiffany Mei, Vinay Kshirsagar, Sam Eure, presented at Bass Connections Showcase, Duke University, April 17, 2019)

Quantifying Gerrymandering (talk by Samuel Eure and Nima Mohammadi, Bass Connections Showcase, Duke University, April 17, 2019)

Project team site