Coombs' method: Difference between revisions

Revision as of 22:47, 23 May 2025

Latest revision as of 15:37, 28 May 2025

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'''Coombs' method''' is a [[ranked voting systems|ranked voting system]]. Like [[Instant-runoff voting|instant-runoff (IRV-RCV)]], Coombs' method is a [[Sequential elimination method|sequential-loser method]], where the last-place finisher according to one method is eliminated in each round. However, unlike in instant-runoff, each round has electors voting against their least-favorite candidate; the candidate ranked last by the most voters is eliminated.<ref name="Grofman">{{Cite journal |last=Grofman |first=Bernard |last2=Feld |first2=Scott L. |date=2004-12-01 |title=If you like the alternative vote (a.k.a. the instant runoff), then you ought to know about the Coombs rule |url=https://www.sciencedirect.com/science/article/abs/pii/S026137940300060X |journal=Electoral Studies |volume=23 |issue=4 |pages=641–659 |doi=10.1016/j.electstud.2003.08.001 |issn=0261-3794|url-access=subscription }}</ref>

The method fails mostseveral [[voting system criteria]], including [[Condorcet winner criterion|Condorcet's majority criterion]], [[Monotonicity criterion|monotonicity]], [[Participation criterion|participation]], and [[Independence of clones criterion|clone-independence]].<ref>{{cite journal |last=Nurmi |first=Hannu |title=Voting Procedures: A Summary Analysis |journal=British Journal of Political Science |volume=13 |issue=2 |pages=181-208 |publisher=Cambridge University Press |date=1983-04-01 |language=English |url=https://www.cambridge.org/core/journals/british-journal-of-political-science/article/abs/voting-procedures-a-summary-analysis/67C52E7250EB4B88018B22D59CAA6908 |doi=10.1017/S0007123400003215 |access-date=2024-05-19 |url-access=subscription }}</ref><ref>{{cite book |last=Nurmi |first=Hannu |title=Comparing Voting systems |publisher=Springer Dordrecht |series= Theory and Decision Library A |volume=3 |edition=Illustrated |date=2012-12-06 |pages=209 |language=English |url= https://link.springer.com/book/10.1007/978-94-009-3985-1?utm_medium=referral&utm_source=google_books&utm_campaign=3_pier05_buy_print&utm_content=en_08082017 |doi= 10.1007/978-94-009-3985-1 |isbn= 9789400939851}}</ref> However, it does satisfy Black's single-peaked [[Median voter property|median voter criterion]].<ref name="Grofman" />{{rp|at=prop. 2}}

== History ==