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Coombs' method: Difference between revisions
Providing an #Example, and linking to Rob LeGrand's voting calculator and linking to a Felsenthal/Tideman paper
(Added some links based on reddit discussion) |
(Providing an #Example, and linking to Rob LeGrand's voting calculator and linking to a Felsenthal/Tideman paper) |
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{{Wikipedia}}
'''Coombs' method''' (or the '''Coombs rule''')<ref>Grofman, Bernard, and Scott L. Feld (2004) [https://dx.doi.org/10.1016/j.electstud.2003.08.001 "If you like the alternative vote (a.k.a. the instant runoff), then you ought to know about the Coombs rule,"] ''Electoral Studies'' '''23''':641-59.</ref> is a [[ranked voting systems|ranked voting system]] created by [[wikipedia:Clyde Coombs|Clyde Coombs]] used for single-winner [[election]]s. Similarly to [[instant-runoff voting]], it uses candidate elimination and redistribution of votes cast for that candidate until one candidate has a majority of votes.
==Example ==
Coombs' method frequently selects the [[Condorcet winner criterion|Condorcet winner]]. However, this does not always happen. For example:
7:a>c>d>b
6:a>d>b>c
3:b>a>c>d
7:b>c>a>d
9:b>c>d>a
4:c>a>d>b
6:d>a>b>c
3:a>c>b>d
This example, placed in [https://cs.angelo.edu/~rlegrand/rbvote/calc.html Rob LeGrand's voting calculator], shows that Coombs arrives at a different result than Condorcet. The example is pulled from a Felsenthal and Tideman paper.<ref>{{Cite journal |last=Felsenthal |first=Dan |last2=Tideman |first2=Nicolaus |date=2013 |title=Varieties of failure of monotonicity and participation under five voting methods |url=https://www.researchgate.net/profile/Dan-Felsenthal/publication/257667897_Varieties_of_failure_of_monotonicity_and_participation_under_five_voting_methods/links/54aec0fb0cf21670b35870a6/Varieties-of-failure-of-monotonicity-and-participation-under-five-voting-methods.pdf?origin=publication_detail|journal=Theory and Decision |language=en |volume=75 |issue=1 |pages=59–77}}</ref>
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