Flaws in the Efficiency Gap

Gerrymandering is returning to the Supreme Court. For the first time in three decades, a federal court invalidated redistricting legislation on the grounds that it constituted a partisan gerrymander in violation of the Fourteenth Amendment. That court relied, in part, on a new tool—the efficiency gap—which some have touted as the means to “end gerrymandering once and for all.” We evaluate this tool and find it wanting. The efficiency gap is neither a cure to the malady of partisan gerrymandering nor even a good idea. Its use by courts may worsen the problem they seek to solve. The foundation for partisan gerrymandering claims is the 1986 case of Davis v. Bandemer, in which a fractured Supreme Court held that partisan gerrymandering is justiciable as a violation of the Equal Protection Clause of the Fourteenth Amendment because it is an attempt to weaken the voting power of a disfavored political party. The ruling has been repeated in every Supreme Court case on partisan gerrymandering since, despite a minority view that partisan gerrymandering should be held to be a political question. However, while these cases have opened the door to challenges, neither Bandemer nor any of the subsequent cases rejected any districting laws as constituting an illegal partisan gerrymander.