Difference between revisions of "River"

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(Added summary of method)
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River is a cloneproof monotonic [[Condorcet_method#Different_ambiguity_resolution_methods|Condorcet ambiguity resolution method]] with similarities to both [[Ranked Pairs]] and [[Cloneproof Schwartz Sequential Dropping]], but when cycles exist, can in rare cases find a different winner than either of the other two methods.
 
River is a cloneproof monotonic [[Condorcet_method#Different_ambiguity_resolution_methods|Condorcet ambiguity resolution method]] with similarities to both [[Ranked Pairs]] and [[Cloneproof Schwartz Sequential Dropping]], but when cycles exist, can in rare cases find a different winner than either of the other two methods.
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Quick summary of method, which is identical to Ranked Pairs except where emphasized:
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* Rank defeats in descending order of winning vote strength.
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* Starting with the strongest defeat, affirm defeats unless a cycle is created ''or a candidate is defeated twice''.
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The result is that only sufficient defeat information to determine the winner is included.
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Because not all defeats are processed, the social ordering is not linear -- in general it is a tree (or river) diagram, with the victor at the base of the river.
  
 
It was first proposed by [[User:Heitzig-j|Jobst Heitzig]] on the [[Election-methods mailing list]]:
 
It was first proposed by [[User:Heitzig-j|Jobst Heitzig]] on the [[Election-methods mailing list]]:
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* [http://lists.electorama.com/pipermail/election-methods-electorama.com/2004-October/014102.html Example using 2004 baseball scores].  This shows how a 14-candidate election winner can be determined much more quickly using River than with RP or Beatpath.
 
* [http://lists.electorama.com/pipermail/election-methods-electorama.com/2004-October/014102.html Example using 2004 baseball scores].  This shows how a 14-candidate election winner can be determined much more quickly using River than with RP or Beatpath.
 
* [http://lists.electorama.com/pipermail/election-methods-electorama.com/2004-April/012678.html Early criticism of the River method].  This shows that the River method violates mono-add-top and mono-remove-bottom
 
* [http://lists.electorama.com/pipermail/election-methods-electorama.com/2004-April/012678.html Early criticism of the River method].  This shows that the River method violates mono-add-top and mono-remove-bottom
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Revision as of 13:04, 2 May 2005

River is a cloneproof monotonic Condorcet ambiguity resolution method with similarities to both Ranked Pairs and Cloneproof Schwartz Sequential Dropping, but when cycles exist, can in rare cases find a different winner than either of the other two methods.

Quick summary of method, which is identical to Ranked Pairs except where emphasized:

  • Rank defeats in descending order of winning vote strength.
  • Starting with the strongest defeat, affirm defeats unless a cycle is created or a candidate is defeated twice.

The result is that only sufficient defeat information to determine the winner is included.

Because not all defeats are processed, the social ordering is not linear -- in general it is a tree (or river) diagram, with the victor at the base of the river.

It was first proposed by Jobst Heitzig on the Election-methods mailing list: