On the complexity of Nash equilibria of action-graph games
SODA '09 Proceedings of the twentieth Annual ACM-SIAM Symposium on Discrete Algorithms
Single-peaked consistency and its complexity
Proceedings of the 2008 conference on ECAI 2008: 18th European Conference on Artificial Intelligence
Complexity of unweighted coalitional manipulation under some common voting rules
IJCAI'09 Proceedings of the 21st international jont conference on Artifical intelligence
Equilibria of plurality voting with abstentions
Proceedings of the 11th ACM conference on Electronic commerce
Graphical models for game theory
UAI'01 Proceedings of the Seventeenth conference on Uncertainty in artificial intelligence
Computing nash equilibria of action-graph games via support enumeration
WINE'11 Proceedings of the 7th international conference on Internet and Network Economics
Convergence of iterative voting
Proceedings of the 11th International Conference on Autonomous Agents and Multiagent Systems - Volume 2
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Voting is widely used to aggregate the different preferences of agents, even though these agents are often able to manipulate the outcome through strategic voting. Most research on manipulation of voting methods studies (1) limited solution concepts, (2) limited preferences, or (3) scenarios with a few manipulators that have a common goal. In contrast, we study voting in plurality elections through the lens of Nash equilibrium, which allows for the possibility that any number of agents, with arbitrary different goals, could all be manipulators. This is possible thanks to recent advances in (Bayes-)Nash equilibrium computation for large games. Although plurality has numerous pure-strategy Nash equilibria, we demonstrate how a simple equilibrium refinement---assuming that agents only deviate from truthfulness when it will change the outcome---dramatically reduces this set. We also use symmetric Bayes-Nash equilibria to investigate the case where voters are uncertain of each others' preferences. This refinement does not completely eliminate the problem of multiple equilibria. However, it does show that even when agents manipulate, plurality still tends to lead to good outcomes (e.g., Condorcet winners, candidates that would win if voters were truthful, outcomes with high social welfare).