Difference between revisions of "River"

From Electowiki
Jump to: navigation, search
Line 13: Line 13:
 
* [http://lists.electorama.com/pipermail/election-methods-electorama.com/2004-April/012671.html slight refinement]
 
* [http://lists.electorama.com/pipermail/election-methods-electorama.com/2004-April/012671.html slight refinement]
 
* [http://lists.electorama.com/pipermail/election-methods-electorama.com/2004-October/013971.html More concise definition].  In this last version, River is defined very similarly to ranked pairs.
 
* [http://lists.electorama.com/pipermail/election-methods-electorama.com/2004-October/013971.html More concise definition].  In this last version, River is defined very similarly to ranked pairs.
* [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 [[Schulze method|Schulze]].
 
* [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
  

Revision as of 18:49, 3 December 2005

River is a cloneproof monotonic Condorcet ambiguity resolution method with similarities to both Ranked Pairs and Schulze, 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: