Pareto efficiency: Difference between revisions

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Line 1: {{wikipedia\|Pareto efficiency}} ~~The~~'''Pareto efficiency''' (frequently referred to as the "'''Pareto criterion'''" or ~~unanimity~~"'''Unanimity criterion'''" in the [[election method]] context) is a basic criterion for evaluating [[voting system\|voting systems]]. It can be defined in this way: {{definition\|If every voter prefers alternative X over alternative Y, then the ~~system~~election method prefers X over Y}} This criterion is important in the context of [[Arrow's impossibility theorem]], since it was one of Arrow's criteria in the theorem. Virtually every devised election method satisfies this criterion. An example of a method which would fail it would be ''Random Candidate'', where some candidate is elected at random, regardless of the submitted votes. Line 11 ⟶ 12: '''Independence of Pareto-dominated alternatives (IPDA)''' says that if one option (X) wins an election, and a new alternative (Y) is added, X will win the election if Y is Pareto-dominated (using the second version of the criterion). The Pareto criterion is ~~Hare-[[PSC]] in~~ the single-winner case of Hare-[[PSC]]. [[Category:Voting system criteria]]