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Press Release · March 5, 2018

California’s district maps are generally fair, increase competitiveness


SAN FRANCISCO, March 5, 2018—Voting districts drawn by California’s independent Citizen Redistricting Commission (CRC) are fair to each major party and have made elections more competitive, according to a new report released today by the Public Policy Institute of California (PPIC).

Overall, the report finds that the CRC plans led to greater competitiveness compared to plans drawn by the state legislature in 2001—which were among the least competitive in the nation. Findings also suggest that Democrats have had a slight edge under the CRC plan, but without the size or durability typical of a gerrymander. While the CRC plans are an improvement, the report suggests ways to avoid potential problems in the future with the use of additional metrics and automated tools to improve mapping.

“California’s Citizen Redistricting Commission largely satisfied expectations that it would produce plans that are fair to each party and more competitive,” said report author and PPIC research fellow Eric McGhee. “The plans have moved California in the opposite direction from many states that have produced less competitive plans in the latest round of redistricting.”

The PPIC report, Assessing California’s Redistricting Commission: Effects on Partisan Fairness and Competitiveness, evaluates election outcomes under the CRC plans using two new measures of partisan gerrymandering, as well as established metrics of competitiveness. It also compares election outcomes to those under the state’s previous plans and places them in a national context. One metric, called the efficiency gap, helps identify a redistricting plan that gives a party more seats even when it has not won more votes. McGhee is the creator of the efficiency gap, and he is the co-creator (with Nicholas Stephanopoulos) of a legal standard that relies on it. Another metric, declination, analyzes the distribution of votes to determine whether district maps are designed to benefit either party.

The report comes at a time when many states are considering adopting a system similar to California’s, particularly in light of two US Supreme Court cases that could establish a new legal standard for partisan gerrymandering. The efficiency gap has played a key role in one of these cases and might be considered as part of any new standard.

Report findings include:

  • The CRC plan for legislative districts is more competitive than the 2001 legislative plan, but is less competitive than most other states’ legislative plans.
  • The plan for congressional districts is more competitive than about 72 percent of the plans in other states. The Democrats have more of an advantage under the CRC plan, but it is a small one.
  • Evidence of partisan advantage is inconsistent over time. Competitiveness is more consistent: every year has been more competitive under the CRC maps than all but one year under the legislature’s maps.

Moving forward, the report recommends that the CRC take partisan data—such as party registration and voting behavior—into account to assess the impact of its plans and avoid any chance of favoring one party over another. It also recommends that the CRC take advantage of new automated redistricting tools that could quickly generate a large number of plans for consideration.


The Public Policy Institute of California is dedicated to informing and improving public policy in California through independent, objective, nonpartisan research. We are a public charity. We do not take or support positions on any ballot measure or on any local, state, or federal legislation, nor do we endorse, support, or oppose any political parties or candidates for public office. Research publications reflect the views of the authors and do not necessarily reflect the views of our funders or of the staff, officers, advisory councils, or board of directors of the Public Policy Institute of California.