Implementing partisan symmetry: Problems and paradoxes

Abstract

We consider the measures of partisan symmetry proposed for practical use in the political science literature, as clarified and developed in [10]. Elementary mathematical manipulation shows the symmetry metrics derived from uniform partisan swing to have surprising properties. To accompany the general analysis, we study measures of partisan symmetry with respect to recent voting patterns in Utah, Texas, and North Carolina, flagging problems in each case. Taken together, these observations should raise major concerns about using quantitative scores of partisan symmetry-including the mean-median score, the partisan bias score, and the more general "partisan symmetry standard"-as the decennial redistricting approaches.

Individual and Differential Harm in Redistricting

“…6 This has been called by some the "Utah paradox" (DeFord et al 2020), though the paradoxical nature is contested as a mistake of using it for description, rather than inference (J. Katz, King, and Rosenblatt Forthcoming).…”

“…7 The differences stem from the efficiency gap considering a vote to be wasted if it is in excess of the 50% threshold needed to win, while the harm framework does not penalize such votes, since every such voter is happily represented by their candidate of choice. This definition of wasted votes is also at the root of other criticisms of the efficiency gap, which note its tendency to penalize proportionality and reward 3-to-1 districts (Bernstein and Duchin 2017;Tam Cho 2017;DeFord et al 2020). While the specific legal requirements for a vote dilution claim will obviously remain front-and-center for court challenges of racial gerrymanders, it is notable that the proposed harm measures unify all three Gingles criteria.…”