
The Complexity of the Possible Winner Problem over Partitioned Preferences
The PossibleWinner problem asks, given an election where the voters' pr...
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Representative Proxy Voting
We study a model of proxy voting where the candidates, voters, and proxi...
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Dealing with incomplete agents' preferences and an uncertain agenda in group decision making via sequential majority voting
We consider multiagent systems where agents' preferences are aggregated...
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Measuring Violations of Positive Involvement in Voting
In the context of computational social choice, we study voting methods t...
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Simulations to Analyze Cellular Voting Systems for Side Effects of Democratic Redistricting
Motivated by the problem of partisan gerrymandering, we introduce an ele...
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Arrow, Hausdorff, and Ambiguities in the Choice of Preferred States in Complex Systems
Arrow's `impossibility' theorem asserts that there are no satisfactory m...
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Proportionality Degree of Multiwinner Rules
We study multiwinner elections with approvalbased preferences. An insta...
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Selecting Matchings via Multiwinner Voting: How Structure Defeats a Large Candidate Space
Given a set of agents with approval preferences over each other, we study the task of finding k matchings fairly representing everyone's preferences. We model the problem as an approvalbased multiwinner election where the set of candidates consists of all possible matchings and agents' preferences over each other are lifted to preferences over matchings. Due to the exponential number of candidates in such elections, standard algorithms for classical sequential voting rules (such as those proposed by Thiele and Phragmén) are rendered inefficient. We show that the computational tractability of these rules can be regained by exploiting the structure of the approval preferences. Moreover, we establish algorithmic results and axiomatic guarantees that go beyond those obtainable in the general multiwinner setting. Assuming that approvals are symmetric, we show that proportional approval voting (PAV), a wellestablished but computationally intractable voting rule, becomes polynomialtime computable, and its sequential variant (seqPAV), which does not provide any proportionality guarantees in general, fulfills a rather strong guarantee known as extended justified representation. Some of our positive computational results extend to other types of compactly representable elections with an exponential candidate space.
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