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Ranked Pairs (RP), also known as the Tideman method, is a tournament-style system of ranked voting first proposed by Nicolaus Tideman in 1987.[1][2]
If there is a candidate who is preferred over the other candidates, when compared in turn with each of the others, the ranked-pairs procedure guarantees that candidate will win. Therefore, the ranked-pairs procedure complies with the Condorcet winner criterion (and as a result is considered to be a Condorcet method).[3]
Ranked pairs begins with a round-robin tournament, where the one-on-one margins of victory for each possible pair of candidates are compared to find a majority-preferred candidate; if such a candidate exists, they are immediately elected. Otherwise, if there is a Condorcet cycle—a rock-paper-scissors-like sequence A > B > C > A—the cycle is broken by dropping the "weakest" elections in the cycle, i.e. the ones that are closest to being tied.[4]
- ^ Tideman, T. N. (1987-09-01). "Independence of clones as a criterion for voting rules". Social Choice and Welfare. 4 (3): 185–206. doi:10.1007/BF00433944. ISSN 1432-217X. S2CID 122758840.
- ^ Schulze, Markus (October 2003). "A New Monotonic and Clone-Independent Single-Winner Election Method". Voting matters (www.votingmatters.org.uk). 17. McDougall Trust. Archived from the original on 2020-07-11. Retrieved 2021-02-02.
- ^ Munger, Charles T. (2022). "The best Condorcet-compatible election method: Ranked Pairs". Constitutional Political Economy. doi:10.1007/s10602-022-09382-w.
- ^ Munger, Charles T. (2022). "The best Condorcet-compatible election method: Ranked Pairs". Constitutional Political Economy. 34 (3): 434–444. doi:10.1007/s10602-022-09382-w.