Optimal Gerrymandering: Sometimes Pack, But Never Crack

Joint with: John N. Friedman - Harvard University

Standard intuitions for optimal gerrymandering involve concentrating one's extreme opponents in "unwinnable" districts ("packing") and spreading one's supporters evenly over "winnable" districts ("cracking"). These intuitions come from models with either no uncertainty about voter preferences, or in which there are only two voter types. In contrast we characterize the solution to a problem in which a gerrymanderer observes a noisy signal of voter preferences from a continuous distribution and creates N districts of equal size to maximize the expected number of districts which she wins. Under mild regularity conditions we show that cracking is never optimal - one's most ardent supporters should be grouped together. Moreover, for sufficiently precise signals the optimal solution involves creating a district which matches extreme

"Republicans" with extreme "Democrats," then continuing to match toward the center of the signal distribution.

For more information, contact Antonio Merlo.