# Difference between revisions of "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 [[Strategic nomination|independence of clones]] criterion which does not properly address rated voting systems and presumes that | + | The '''Independence of Equivalent Candidates criterion''' was devised in 2005 by Thomas Smith. It was inspired by the inadequate definition of the [[Strategic nomination|independence of clones]] criterion which does not properly address rated voting systems and falsely presumes that correlated candidates are necessarily equivalent to each other. This criterion is a theoretical, rather than a practical criterion, and is used to describe the susceptibility of voting methods to the influence of candidates that are perceived by all voters as equivalent. |

− | 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 | + | 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 equally. |

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. | 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. |

## Revision as of 15:32, 20 September 2005

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 falsely presumes that correlated candidates are necessarily equivalent to each other. This criterion is a theoretical, rather than a practical criterion, and is used to describe the susceptibility of voting methods to the influence of candidates that are perceived by all voters as equivalent.

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 equally.

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.