Rank aggregation methods for the Web
Proceedings of the 10th international conference on World Wide Web
Computers and Intractability: A Guide to the Theory of NP-Completeness
Computers and Intractability: A Guide to the Theory of NP-Completeness
Proceedings of the Seventeenth National Conference on Artificial Intelligence and Twelfth Conference on Innovative Applications of Artificial Intelligence
Efficient similarity search and classification via rank aggregation
Proceedings of the 2003 ACM SIGMOD international conference on Management of data
Multi-agent planning as a dynamic search for social consensus
IJCAI'93 Proceedings of the 13th international joint conference on Artifical intelligence - Volume 1
How hard is bribery in elections?
Journal of Artificial Intelligence Research
Using complexity to protect elections
Communications of the ACM
The Clarke tax as a consensus mechanism among automated agents
AAAI'91 Proceedings of the ninth National conference on Artificial intelligence - Volume 1
Incompleteness and incomparability in preference aggregation: Complexity results
Artificial Intelligence
Multimode control attacks on elections
Journal of Artificial Intelligence Research
Determining possible and necessary winners under common voting rules given partial orders
Journal of Artificial Intelligence Research
Winner determination in voting trees with incomplete preferences and weighted votes
Autonomous Agents and Multi-Agent Systems
Computing the margin of victory for various voting rules
Proceedings of the 13th ACM Conference on Electronic Commerce
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We consider the scenario of a parliament that is going to vote on a specific important issue. The voters are grouped in parties, and all voters of a party vote in the same way. The expected winner decision is known, because parties declare their intentions to vote, but before the actual vote takes place some voters may leave the leading party to join other parties. We investigate the computational complexity of the problem of determining how many voters need to leave the leading party before the winner changes. We consider both positional scoring rules (plurality, veto, k-approval, k-veto, Borda) and Condorcet-consistent methods (maximin, Copeland), and we study two versions of the problem: a pessimistic one, where we want to determine the maximal number of voters that can leave the leading party without changing the winner; and an optimistic one, where we want the minimal number of voters that must leave the leading party to be sure the winner will change. These two numbers provide a measure of the threat to the expected winner, and thus to the leading party, given by losing some voters. We show that for many positional scoring rules these problems are easy (except for the optimistic version with k-approval,for k at least 3, and Borda). Instead, for Condorcet-consistent rules, they are both computationally difficult, with both Maximin and Copeland.