User:Cymru/Independence of equivalent candidates criterion

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The Independence of Equivalent Candidates criterion was devised in 2005 by Thomas Smith. It was inspired by the inadequate definition of the independence of clones criterion which does not properly address rated voting systems and presumes that equivalent candidates are identical or very similar to each other.

Equivalent candidates are a group of candidates that are supportively ranked in adjacent positions, where equal ranking is not allowed, or equally ranked or rated, where equality is allowed, on every cast ballot. Thus, an approved and a disapproved candidate can never be "clones" as they are not rated equivalently.

A voting method is said to be independent of equivalent candidates if the addition or removal of a equivalent candidate from a particular set of equivalent candidates in the tally, would only change the winner to another member of the set, if the original winner was a member of that set.

Methods that satisfy this criterion are approval voting, range voting, Bucklin voting, Schulze method, and Instant-runoff voting.

Independence of equivalent candidates is a weakened form of the independence of irrelevant alternatives criterion.