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This article explores computational methods for electing committees and maximizing voter satisfaction in social choice scenarios. It discusses various techniques such as approval ballots and fixed-size minimax, and highlights the challenges in computing optimal outcomes.
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Computational Social Choice - or - Political Science meets Computer Science Ron K. Cytron http://www.cs.wustl.edu/~cytron/ Joint work with Lorrie Cranor (Wash U Ph.D. student, now at CMU) Rob LeGrand (Wash U Ph.D. student, now at Angelo State) 16 May 2014
Some voting results are difficult to compute • Voters say yes or no to each of k candidates • Elect a subset of the candidates so that • Least pleased voter is as happy as possible • Bring as many people “forward” as possible
Electing a committee from approval ballots[ Brams, NYU ] approves of candidates 4 and 5 11110 00011 k = 5 candidates n = 6 ballots 01111 00111 10111 00001 • What’s the best committee of size m = 2?
Sum of Hamming distances How happy? 11110 00011 m = 2 winners 2 4 4 5 01111 11000 00111 4 3 sum = 22 10111 00001
Fixed-size minisum How happy? 11110 00011 m = 2 winners 4 0 2 1 01111 00011 00111 2 1 sum = 10 10111 00001 • Minisum elects winner set with smallest sumscore • Easy to compute (pick candidates with most approvals)
Maximum Hamming distance 11110 00011 m = 2 winners 4 0 2 1 01111 00011 00111 2 1 sum = 10 max = 4 10111 00001
Fixed-size minimax [Brams, Kilgour & Sanver ’04] 11110 00011 m = 2 winners 2 2 2 1 01111 00110 00111 2 3 sum = 12 max = 3 10111 00001 • Minimax elects winner set with smallest maxscore • Hard to compute! Currently have to try all outcomes