Measures of gerrymandering — real or bogus?

As courts in Pennsylvania and around the country consider cases charging partisan political gerrymandering, the National Constitution Center in Philadelphia recently assembled prominent experts and participants in the battles to talk about the political and constitutional issues.

Courts have long acknowledged gerrymandering exists, but they have lacked a reliable standard for measuring just how much of a political edge a particular legislative map gives to one party.

In the case that’s captured the most national attention, a federal court struck down boundaries drawn by the Wisconsin state legislature as biased in favor of Republicans, and the U.S. Supreme Court has heard arguments on the appeal.

In the Wisconsin case, a new mathematical formula for measuring gerrymandering made a difference.

It considers election results and measures how “efficient” each party is with its votes while running in the boundaries at issue. If Democrats are packed into a few districts they won by big margins — while Republicans are strategically spread to capture many districts by narrow spreads — the resulting “efficiency gap” measures the bias of the political boundaries. At least, that’s the idea.

Among the panelists at the Dec. 11 Constitution Center event were Nicholas Stephanopoulos, a University of Chicago law professor who helped develop the efficiency gap measurement, and Erin Murphy, an election lawyer who defended the Wisconsin map before the Supreme Court.

The audio here captures a portion of their debate. You can see a video of their discussion, and a separate panel of three experts on the political dimensions of the issue, moderated by National Constitution Center President Jeffrey Rosen on YouTube.