Opinion | How Computers Turned Gerrymandering Into a Science

December 18, 2017

How Computers Turned Gerrymandering Into a Science
https://www.NYTimes.com/2017/10/06/opinion/sunday/computers-gerrymandering-wisconsin.html MCMC random walks evaluate possible redistricting swaps, producing complex boundaries. Eventually, we may get fractal electoral maps!

The clustering of Democrats in cities does indeed give the Republicans an edge. But it’s a much smaller advantage than the turbo-boost the current map provides, as the Duke paper demonstrates. The main tool in the Duke paper is a method called the “Markov chain Monte Carlo” algorithm. Starting from the current Wisconsin district map, it makes a sequence of random changes, swapping wards from one district to an adjacent one, carrying out a “random walk” through the set of all possible maps. Completely unconstrained changes would create crazy-looking districts, so it weights its changes in favor of traditional districting criteria.