"The efficiency gap": understanding the math behind a crucial Supreme Court gerrymandering case

Last October, the Supreme Court heard argument in Gill v. Whitford, a Wisconsin gerrymandering case that has far-reaching implications for the November midterms in 2018; the court is expected to rule next June.

Anti-gerrymandering activists have their hopes pinned on a mathematical voting fairness model developed by the Metric Geometry and Gerrymandering Group at Tufts, where mathematicians, led by Moon Duchin, have cut through much of the confusion and contradictions in the gerrymandering debate with the crucial idea of "efficiency gaps" in voting.

In an excellent explainer, Patrick Honner lays out the math behind the argument. It's an important, smart and crisp way of describing how to fairly design electoral districts, and it could change the destiny of America and the world.

Start by imagining a state with 200 voters, of whom 100 are loyal to party A and 100 to party B. Let's suppose the state needs to elect four representatives and so must create four districts of equal electoral size.

Imagine that you have the power to assign voters to any district you wish. If you favor party A, you might distribute the 100 A voters and 100 B voters into the four districts like this…

The Math Behind Gerrymandering and Wasted Votes [Patrick Honner/Wired]

(Image: Scott Martin/Quanta Magazine)