Prof. Simon Jackman of Stanford University, a political statistician, has done a watershed study of all elections in the period since the 1970 census, the first census since one-person one-vote became the law of the land. Because full elections data was not available in some states and other local peculiarities, he had to eliminate nine states. The result was an analysis of the efficiency gap in 786 state legislative elections in 41 states from 1972-2014.
And what he found puts the Wisconsin situation into stunning perspective. Looking at Wisconsin’s EG (efficiency gap) of 13 percent in 2012 and 10 percent in 2014, he concludes that in “the entire set of 786 state legislative elections” in 41 states, no other redistricting generated “an initial two-election sequence of EG scores that are each as large as those observed in Wisconsin.” In short, the gerrymandering in Wisconsin as measured by the efficiency gap is “virtually without historical precedent,” he concludes.