AP analysis finds partisan gerrymandering benefits Republicans more than Democrats

An analysis by The Associated Press shows that partisan redistricting of congressional and state House districts has given Republicans a significant edge in recent years.

How significant? “The analysis found four times as many states with Republican-skewed state House or Assembly districts than Democratic ones,” reports AP's David A. Lieb. As for the U.S. House, “Among the two dozen most populated states that determine the vast majority of Congress, there were nearly three times as many with Republican-tilted U.S. House districts.”

The analysis comes in the wake of the U.S. Supreme Court’s announcement that it would hear a case this fall challenging the legality of Wisconsin’s legislative districts. A lower court ruled that the districts violated Democratic voters’ right to equal representation because the percentage of seats won by Democrats was much smaller than the percentage of votes cast for Democrats. If the Supreme Court upholds the decision, it could cause drastic changes in the way districts are drawn across the US. Other cases are also under consideration.

Voting districts are redrawn every 10 years following the U.S. Census. According to AP's analysis, partisan gerrymandering became rampant in recent years, peaking in 2012.

The analysis was based on a formula that computes the “efficiency gap”, which quantifies gerrymandering far more accurately than the traditionally used metric of “partisan bias.” The formula was developed by University of Chicago law professor Nick Stephanopoulos and nonpartisan researcher Eric McGhee.