On Coalitional Manipulation for Multiwinner Elections: Shortlisting
نویسندگان
چکیده
Shortlisting of candidates—selecting a group of “best” candidates—is a special case of multiwinner elections. We provide the first in-depth study of the computational complexity of strategic voting for shortlisting based on the most natural and simple voting rule in this scenario, `-Bloc (every voter approves ` candidates). In particular, we investigate the influence of several tie-breaking mechanisms (e.g. pessimistic versus optimistic) and group evaluation functions (e.g. egalitarian versus utilitarian) and conclude that in an egalitarian setting strategic voting may indeed be computationally intractable regardless of the tie-breaking rule. We provide a fairly comprehensive picture of the computational complexity landscape of this neglected scenario.
منابع مشابه
What Do Multiwinner Voting Rules Do? An Experiment Over the Two-Dimensional Euclidean Domain
We visualize aggregate outputs of popular multiwinner voting rules—SNTV, STV, Bloc, k-Borda, Monroe, Chamberlin– Courant, and PAV—for elections generated according to the two-dimensional Euclidean model. We consider three applications of multiwinner voting, namely, parliamentary elections, portfolio/movie selection, and shortlisting, and use our results to understand which of our rules seem to ...
متن کاملThe Condorcet Principle for Multiwinner Elections: From Shortlisting to Proportionality
We study two notions of stability in multiwinner elections that are based on the Condorcet criterion. The first notion was introduced by Gehrlein: A committee is stable if each committee member is preferred to each non-member by a (possibly weak) majority of voters. The second notion is called local stability (introduced in this paper): A size-k committee is locally stable in an election with n...
متن کاملAn Empirical Study of Borda Manipulation
We study the problem of coalitional manipulation in elections using the unweighted Borda rule. We provide empirical evidence of the manipulability of Borda elections in the form of two new greedy manipulation algorithms based on intuitions from the bin-packing and multiprocessor scheduling domains. Although we have not been able to show that these algorithms beat existing methods in the worst-c...
متن کاملComplexity of Strategic Behavior in Multi-Winner Elections
Although recent years have seen a surge of interest in the computational aspects of social choice, no specific attention has previously been devoted to elections with multiple winners, e.g., elections of an assembly or committee. In this paper, we characterize the worst-case complexity of manipulation and control in the context of four prominent multiwinner voting systems, under different formu...
متن کاملAn NTU Cooperative Game Theoretic View of Manipulating Elections
Social choice theory and cooperative (coalitional) game theory have become important foundations for the design and analysis of multiagent systems. In this paper, we use cooperative game theory tools in order to explore the coalition formation process in the coalitional manipulation problem. Unlike earlier work on a cooperative-game-theoretic approach to the manipulation problem [2], we conside...
متن کامل