By Jay Cost
The Weekly Standard
October 18, 2017

Earlier this month, the Supreme Court heard oral arguments in Gill v. Whitford, a case in which University of Wisconsin professor William Whitford and a group of plaintiffs (all Democratic voters in the state) contend that the drawing up of Wisconsin’s state legislative districts was an unconstitutional gerrymander.

The Supreme Court has intervened in gerrymandering complaints in the past, but those cases had to do with racial discrimination or malapportionment. That is, the Court has struck down legislative maps that distribute black voters in ways that minimize their electoral power. In the Wisconsin case, race and ethnicity are not at issue, at least not directly. The plaintiffs are asking the Court to invalidate district lines drawn by the state legislature in 2011 because those lines favor Republicans over Democrats.

Based on the oral arguments, the case is another that divides the Court along ideological lines. The four conservative justices—Chief Justice John Roberts, Clarence Thomas, Samuel Alito, and Neil Gorsuch—seem skeptical that the Court should intervene in such matters. It is better, instead, to leave partisan gerrymanders to the political process. The liberals—Ruth Bader Ginsburg, Stephen Breyer, Sonia Sotomayor, and Elena Kagan—appear eager to involve the Court in the process. Once again, that leaves Justice Anthony Kennedy in the middle, the crucial fifth vote who will decide which way the Court swings.

Kennedy has previously expressed openness to the Court’s involving itself in resolving partisan gerrymandering. In Vieth v. Jubelirer (2004), though the Court declined to rule on the constitutionality of Pennsylvania’s congressional redistricting, Kennedy indicated that the justices might have a role to play if they could find a workable standard to apply.

This is what makes the Wisconsin case especially important. The plaintiffs claim to have put forward such a standard—based on a metric known as the “efficiency gap”—that, they argue, is a simple, intuitive, and broadly applicable tool to find the effects of a gerrymander.

However, the plaintiffs are wrong. The efficiency gap is an interesting but deeply problematic metric that should not be imposed by the judiciary. If Kennedy and the liberal justices were to adopt it as the centerpiece of a test to adjudicate partisan complaints about the drawing of political districts, it could have profound, unintended, and controversial consequences on legislatures throughout the country.

At first blush, the efficiency gap seems quite straightforward. The whole approach hinges on the concept of “wasted” votes. For instance, if a party gets 75 percent of the votes in state legislative contests but wins only 50 percent of the seats, then 25 percent of the vote has been “wasted,” or cast in excess of the final seat totals the party won. Generally speaking, the efficiency gap is calculated by comparing votes to seats, and the plaintiffs are asking the Court to use it to decide whether district maps are presumptively valid or invalid. They claim that if the efficiency gap exceeds a certain threshold, then it is likely because the party in charge of drawing the district lines has cheated the opposition.

There are a number of problems with this. The most immediate concern is that the efficiency gap has simply not undergone sufficient peer review.

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