The Rising Incumbent Reelection Rates: What’s Gerrymandering Got to Do with It

The probability that an incumbent in the United States House of Representatives is reelected has risen dramatically over the last half-century; it now stands at more than 98%. A number of authors and commentators claim that this rise is due to an increase in bipartisan gerrymandering in favor of incumbents. Using a regression discontinuity approach, we \u85nd evidence of the opposite e¤ect. All else equal, changes in redistrict-ing have reduced the probability of incumbent reelection over time. The timing of this e¤ect is consistent with the hypothesis that legal constraints on gerrymandering, such as the Voting Rights Act, have become tighter over time. Incumbent gerrymandering may well be a contributor to incumbent reelection rates, but it is less so than in the past