Independence of irrelevant alternatives: Difference between revisions
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In [[voting system]]s, '''independence of irrelevant alternatives''' is the property some voting systems have that, if one option (X) wins the election, and a new alternative (Y) is added, only X or Y will win the election.
{{definition | If every voter's preference between X and Y remains unchanged, then the group's preference between X and Y will also remain unchanged with the addition of a new candidate}}
[[Condorcet method]]s necessarily fail this criterion, although some, such as [[Ranked Pairs]], satisfy a related but weaker criterion known as [[local independence of irrelevant alternatives]]. [[Borda count]], [[Coombs' method]], and [[Instant-runoff voting]] fail. [[Range voting]], [[approval voting]], and [[majority judgment]] satisfy the criterion.
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