Difference between revisions of "Ranked Approval Voting"

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'''Ranked Approval Voting''' is an election method combining a ranked ballot with an approval measure. Possibly Kevin Venzke was the first to suggest it on the election methods mailing list, in 2003. It was given the name "Ranked Approval Voting" by Russ Paielli. At present, this method has not been peer-reviewed and submitted to rigorous analysis.
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'''Ranked Approval Voting''' (RAV) is an election method combining a ranked ballot with an approval measure. Kevin Venzke may have been the first to suggest it on the election methods mailing list, in 2003 (''need to provide link to list posting here --Araucaria''). It was given the name "Ranked Approval Voting" by Russ Paielli.
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RAV finds the same winner as [[Definite Majority Choice]].
  
 
== Ballot Format ==
 
== Ballot Format ==
  
The voter ranks the candidates. Approval could be indicated by a cutoff placed by the voter, or it can be implicit that the approved candidates are all those that the voter chooses to rank.
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To implement RAV, a voter uses a [[Preferential voting|ranked ballot]].  By default, any ranked candidates are considered approved.   Depending on implementation, the voter may also add an [[Approval Cutoff|approval cutoff]] to indicate that some of the ranked candidates are not approved.
  
 
== Procedure ==
 
== Procedure ==
  
Ranked Approval Voting is a '''[[Condorcet method]]''', which means it always elects a "Condorcet winner" if one exists. A Condorcet winner is a candidate whom more voters rank above ''Y'' than vice versa, given any other candidate ''Y''.
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Ballots are tabulated into a [[Condorcet_method#Counting_with_matrices|pairwise matrix]].
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Repeat until a winner is found:
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* Search for a candidate who is not defeated by any other non-eliminated candidates.  If one is found, this is the RAV winner..
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* If no RAV winner exists, the candidate with the least approval is eliminated —his pairwise contests are no longer considered.
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The process repeats until some non-eliminated candidate pairwise defeats every other non-eliminated candidate.
  
If a Condorcet winner doesn't initially exist, then the candidate with the least approval is eliminated such that his pairwise contests are no longer considered. These eliminations continue until a Condorcet winner is created; that is, until some non-eliminated candidate has pairwise wins over every other non-eliminated candidate. Then this candidate is elected.
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Ranked Approval Voting is a '''[[Condorcet method]]''', which means it always finds the [[Condorcet Criterion|Condorcet winner]] if one exists. A Condorcet winner is the candidate who, when compared in turn with each of the other candidates, is preferred by more voters to the other candidate. This implies that a majority of ballots rank the CW above any other candidate.
  
 
== Advantages ==
 
== Advantages ==
  
Ranked Approval Voting inherently satisfies the [[Smith set|Smith criterion]], without requiring an explicit step to reduce to the Smith set.
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Ranked Approval Voting satisfies the [[Smith set|Smith criterion]] without requiring an explicit step to reduce to the Smith set.
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[[Category:Condorcet method]]

Revision as of 16:00, 10 May 2005

Ranked Approval Voting (RAV) is an election method combining a ranked ballot with an approval measure. Kevin Venzke may have been the first to suggest it on the election methods mailing list, in 2003 (need to provide link to list posting here --Araucaria). It was given the name "Ranked Approval Voting" by Russ Paielli.

RAV finds the same winner as Definite Majority Choice.

Ballot Format

To implement RAV, a voter uses a ranked ballot. By default, any ranked candidates are considered approved. Depending on implementation, the voter may also add an approval cutoff to indicate that some of the ranked candidates are not approved.

Procedure

Ballots are tabulated into a pairwise matrix.

Repeat until a winner is found:

  • Search for a candidate who is not defeated by any other non-eliminated candidates. If one is found, this is the RAV winner..
  • If no RAV winner exists, the candidate with the least approval is eliminated —his pairwise contests are no longer considered.

The process repeats until some non-eliminated candidate pairwise defeats every other non-eliminated candidate.

Ranked Approval Voting is a Condorcet method, which means it always finds the Condorcet winner if one exists. A Condorcet winner is the candidate who, when compared in turn with each of the other candidates, is preferred by more voters to the other candidate. This implies that a majority of ballots rank the CW above any other candidate.

Advantages

Ranked Approval Voting satisfies the Smith criterion without requiring an explicit step to reduce to the Smith set.