Ranked Pairs: Difference between revisions

Line 1:

'''Ranked Pairs''' (RP) or ~~'''Tideman'''~~ ~~(named~~ ~~after~~ [[Nicolaus Tideman]]) is a [[voting system]] that selects a single winner using votes that express preferences. RP can also be used to create a sorted list of winners. RP passes the [[Smith criterion]] and [[Condorcet ~~Criterion~~]], ~~and~~ is ~~by definition~~ a ~~'''~~[[Condorcet method]]~~'''~~. RP has many variations such as the [[Maximize Affirmed Majorities]] (MAM) and [[Maximum Majority Voting]] (MMV) voting methods.

The "'''Ranked Pairs'''" method (sometimes abbreviated as "RP") was created in 1987 by [[Nicolaus Tideman]]. It is a [[voting system]] that selects a single winner using votes that express preferences. The ranked-pairs method can also be used to create a sorted list of winners. Ranked Pairs passes the [[Smith criterion]] and the [[Condorcet winner criterion]] (thus making it a "[[Condorcet method]]"). The ranked-pairs method has many variations such as the "[[Maximize Affirmed Majorities]]" (or "MAM") and "[[Maximum Majority Voting]]" (or "MMV") voting methods.

== Procedure ==

The RP procedure is as follows:

The ranked-pairs procedure works as follows:

# Tally the vote count comparing each pair of candidates, and determine the winner of each pair (provided there is not a tie)

# Sort (rank) each pair, by the largest margin of victory first to smallest last.

Line 12:

See the [[Ranked pairs#Notes|Notes]] section for information on finding the Ranked Pairs winner without constructing a graph.

RP can also be used to create a sorted list of preferred candidates.

Ranked Pairs can also be used to create a sorted list of preferred candidates. To create a sorted list, repeatedly use the procedure to do the following:

~~To create a sorted list, repeatedly use RP to~~ select a winner,

* select a winner,

remove that winner from the list of candidates,

* remove that winner from the list of candidates,

and repeat (to find the next runner up, and so forth). A simpler way to create the sorted list is simply to run RP once, and then use the resulting [[Condorcet ranking]] (when ignoring the defeats that were ignored by the RP procedure) as the RP ranking.

* ...and repeat (to find the next runner up, and so forth)

A simpler way to create the sorted list is simply to run Ranked Pairs once, and then use the resulting [[Condorcet ranking]] (when ignoring the defeats that were ignored by the ranked-pairs procedure) as the ranked-pairs ranking.

=== Tally ===