Ranked Choice Including Pairwise Elimination: Difference between revisions

The RCIPE STV method extends the single-winner RCIPE method to fill multiple equivalent seats.

== RCIPE STV ==

The RCIPE method can be extended to elect multiple candidates, such as when electing non-partisan members of a city council, or when electing two (or more) representatives from the same district.

The RCIPE STV method modifies the Single Transferable Vote (STV) method in the following ways:

* During each round of counting either one candidate is elected or one candidate is eliminated, but not both in the same round.

* If more than one candidate has enough transferred votes to exceed the quota for that round, the candidate with the highest transferred-vote count is elected.

* The ballots that support an elected candidate with transferred votes are proportionally reduced in influence according to any excess beyond the quota. Specifically the reduced influence amount equals the number of votes beyond the quota vote count divided by the count of the supporting ballots. If decimal values are not allowed, these supporting ballots are reduced to zero influence. Any supporting ballots that already have reduced influence are reduced to zero influence after any secondary partial support.

* After each counting round all the ballots are re-counted and transferred to the highest-ranked candidate (on that ballot) who has not yet been elected or eliminated. Some ballots will have reduced influence, or no influence, if they already contributed partial support to one or two candidates who have been elected.

* Ballots on which two or more remaining (not-yet-elected and not-yet-eliminated) candidates are ranked at the same preference level are temporarily categorized as "currently not available to be transferred" for the remainder of that counting round.

* If no candidate is elected during a counting round, and there is a pairwise losing candidate during that round, the pairwise losing candidate is eliminated instead of eliminating the candidate with the fewest transferred votes. During pairwise counting the ballots that have reduced influence are counted according to that reduced influence. When checking for a pairwise losing candidate, the ballots that are categorized as "currently not available to be transferred" are included in the pairwise count, but some of these ballots may have partial influence rather than full influence.

Any reasonable quota can be chosen for the RCIPE STV method.