Ranked Choice Including Pairwise Elimination: Difference between revisions
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'''Ranked Choice Including Pairwise Elimination''' (abbreviated as '''RCIPE''' which is pronounced "recipe") is an election vote-counting method that uses ranked ballots and eliminates '''pairwise losing candidates''' ([[Condorcet loser criterion|Condorcet losers]]) when they occur, and otherwise eliminates the candidate who currently has the |
'''Ranked Choice Including Pairwise Elimination''' (abbreviated as '''RCIPE''' which is pronounced "recipe") is an election vote-counting method that uses ranked ballots and eliminates '''pairwise losing candidates''' ([[Condorcet loser criterion|Condorcet losers]]) when they occur, and otherwise eliminates the candidate who currently has the smallest top-choice count. |
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This method modifies [[Instant-Runoff Voting|instant runoff voting]] (IRV) by adding the elimination of Condorcet losers. This addition would have prevented the failure of instant-runoff voting to elect the most popular candidate in the 2009 mayoral election in Burlington, Vermont. |
This method modifies [[Instant-Runoff Voting|instant runoff voting]] (IRV) by adding the elimination of Condorcet losers. This addition would have prevented the failure of instant-runoff voting to elect the most popular candidate in the 2009 mayoral election in Burlington, Vermont. |
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If an elimination round has a Condorcet loser (a '''pairwise losing candidate'''), this candidate is eliminated as the least-popular candidate. The Condorcet loser is the candidate who would lose every one-on-one contest against each and every other candidate. |
If an elimination round has a Condorcet loser (a '''pairwise losing candidate'''), this candidate is eliminated as the least-popular candidate. The Condorcet loser is the candidate who would lose every one-on-one contest against each and every other candidate. |
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If an elimination round does not have a Condorcet loser, the candidate who has the |
If an elimination round does not have a Condorcet loser, the candidate who has the smallest top-choice count is eliminated. A candidate's top-choice count is the count of how many ballots rank that candidate highest compared to the other remaining candidates. |
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Unlike instant-runoff voting, which ends when a candidate reaches majority support, the eliminations continue until only a single candidate remains. |
Unlike instant-runoff voting, which ends when a candidate reaches majority support, the eliminations continue until only a single candidate remains. |
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Importantly, the runner-up candidate does not deserve to win any kind of elected seat. This means this method is not suitable for filling multiple seats, such as on a city council or in a multi-member district. |
Importantly, the runner-up candidate does not deserve to win any kind of elected seat. This means this method is not suitable for filling multiple seats, such as on a city council or in a multi-member district. |
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To avoid spoiled ballots in elections where the voter uses a pen or marker to mark their paper ballot, more than one candidate can be marked at the same ranking level. When an elimination round involves two or more remaining highest-ranked candidates, |
To avoid spoiled ballots in elections where the voter uses a pen or marker to mark their paper ballot, more than one candidate can be marked at the same ranking level. When an elimination round involves a ballot that has two or more remaining highest-ranked candidates, that ballot's single vote is split equally among these candidates. This splitting of a single vote can be done using fractions or decimal numbers that do not exceed a total of one vote per ballot. |
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Also to avoid spoiled ballots, if a voter marks more than one ranking level for the same candidate, only the highest-marked ranking level is used during counting. |
Also to avoid spoiled ballots, if a voter marks more than one ranking level for the same candidate, only the highest-marked ranking level is used during counting. |
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== Tie breaker == |
== Tie breaker == |
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If two or more candidates have the same smallest top-choice count, this tie is resolved by eliminating the candidate with the largest pairwise opposition count, which is determined by counting on each ballot the number of not-yet-eliminated tied candidates who are ranked above that candidate, and adding |
If two or more candidates have the same smallest top-choice count, this tie is resolved by eliminating the candidate with the largest pairwise opposition count, which is determined by counting on each ballot the number of not-yet-eliminated tied candidates who are ranked above that candidate, and adding these numbers across all the ballots. |
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If there is a tie for the largest pairwise opposition count, this tie is resolved by eliminating the candidate with the smallest pairwise support count, which is determined by counting on each ballot the number of not-yet-eliminated tied candidates who are ranked above that candidate, and adding |
If there is a tie for the largest pairwise opposition count, this tie is resolved by eliminating the candidate with the smallest pairwise support count, which is determined by counting on each ballot the number of not-yet-eliminated tied candidates who are ranked above that candidate, and adding these numbers across all the ballots. |
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Note that the pairwise opposition count and pairwise support count are calculated using only the candidates who are currently tied. This means that ballot information about eliminated candidates and not-tied candidates is ignored when resolving ties. |
Note that the pairwise opposition count and pairwise support count are calculated using only the candidates who are currently tied. This means that ballot information about eliminated candidates and not-tied candidates is ignored when resolving ties. |
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