Difference between revisions of "River"
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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: | ||
| + | * 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''. | ||
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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:
- First proposal
- slight refinement
- More concise definition. In this last version, River is defined very similarly to ranked pairs.
- 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.
- Early criticism of the River method. This shows that the River method violates mono-add-top and mono-remove-bottom
