Copeland voting: ties matter
Piotr Faliszewski,Edith Hemaspaandra,Henning Schnoor +2 more
- 12 May 2008
- pp 983-990
TL;DR: This work shows that the problem of manipulation for unweighted Copelandα elections is NP-complete even if the size of the manipulating coalition is limited to two, and is the first one where an election system originally known to be vulnerable to manipulation via a single voter is shown to be resistant to manipulation through a coalition of a constant number of voters.
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Abstract: We study the complexity of manipulation for a family of election systems derived from Copeland voting via introducing a parameter α that describes how ties in head-to-head contests are valued. We show that the thus obtained problem of manipulation for unweighted Copelandα elections is NP-complete even if the size of the manipulating coalition is limited to two. Our result holds for all rational values of α such that 0
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Citations
Handbook of Computational Social Choice
TL;DR: This handbook, written by thirty-six prominent members of the computational social choice community, covers the field comprehensively and offers detailed introductions to each of the field's major themes.
Llull and Copeland voting computationally resist bribery and constructive control
TL;DR: Among systems with a polynomial-time winner problem, Copeland voting is the first natural election system proven to have full resistance to constructive control and vulnerability results for microbribery are proven via a novel technique involving min-cost network flow.
Determining possible and necessary winners under common voting rules given partial orders
Lirong Xia,Vincent Conitzer +1 more
TL;DR: The complexity of possible/necessary winner problems for the following common voting rules are completely characterized: a class of positional scoring rules (including Borda), Copeland, maximin, Bucklin, ranked pairs, voting trees, and plurality with runoff.
How hard is bribery in elections
TL;DR: This work obtains both polynomial-time bribery algorithms and proofs of the intractability of bribery, and results show that the complexity of bribery is extremely sensitive to the setting.
Computational Social Choice
Felix Brandt,Ulle Endriss +1 more
- 01 Jan 2012
TL;DR: The Gibbard-Satterthwaite Impossibility and Computational Hardness of Manipulation as mentioned in this paper are two of the main obstacles in voting rule-based election process, and they have been studied extensively in the literature.
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Single Transferable Vote Resists Strategic Voting
John J. Bartholdi,James B. Orlin +1 more
- 06 Sep 2015
TL;DR: Evidence that Single Tranferable Vote (STV) is computationally resistant to manipulation is given and it is proved that it is NP-complete to recognize when an STV election violates monotonicity, suggesting that non-monotonicity in STV elections might be perceived as less threatening since it is in effect “hidden” and hard to exploit for strategic advantage.