PP-2020-17: Analysing Irresolute Multiwinner Voting Rules with Approval Ballots via SAT Solving

PP-2020-17: Kluiving, Boas and de Vries, Adriaan and Vrijbergen, Pepijn and Boixel, Arthur and Endriss, Ulle (2020) Analysing Irresolute Multiwinner Voting Rules with Approval Ballots via SAT Solving. [Pre-print]

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Suppose you want to design a voting rule that can be used to elect a committee or parliament by asking each voter to approve of a subset of the candidates standing. There are several properties you may want that rule to satisfy. First, voters should enjoy some form of proportional representation. Second, voters should not have an incentive to misrepresent their preferences. Third, outcomes should be Pareto efficient. We show that it is impossible to design a voting rule that satisfies all three properties. We also explore what possibilities there are when we weaken our requirements. Of special interest is the methodology we use, as a significant part of the proof is outsourced to a SAT solver. While prior work has considered similar questions for the special case of resolute voting rules, which do not allow for ties between outcomes, we focus on the fact that, in practice, most voting rules allow for the possibility of such ties.

Item Type: Pre-print
Report Nr: PP-2020-17
Series Name: Prepublication (PP) Series
Year: 2020
Uncontrolled Keywords: Computational Social Choice; Voting Theory; Automated Reasoning
Subjects: Computation
Depositing User: Ulle Endriss
Date Deposited: 06 Sep 2020 06:46
Last Modified: 06 Sep 2020 06:46
URI: https://eprints.illc.uva.nl/id/eprint/1752

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