Aggregating Incomplete Pairwise Preferences by Weight

Aggregating Incomplete Pairwise Preferences by Weight

Zoi Terzopoulou, Ulle Endriss

Proceedings of the Twenty-Eighth International Joint Conference on Artificial Intelligence
Main track. Pages 595-601. https://doi.org/10.24963/ijcai.2019/84

We develop a model for the aggregation of preferences that do not need to be either complete or transitive. Our focus is on the normative characterisation of aggregation rules under which each agent has a weight that depends only on the size of her ballot, i.e., on the number of pairs of alternatives for which she chooses to report a relative ranking. We show that for rules that satisfy a restricted form of majoritarianism these weights in fact must be constant, while for rules that are invariant under agents with compatible preferences forming pre-election pacts it must be the case that an agent's weight is inversely proportional to the size of her ballot. 
Keywords:
Agent-based and Multi-agent Systems: Computational Social Choice
Agent-based and Multi-agent Systems: Voting