Majority Choice Approval: Difference between revisions
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== How does it work? ==
Voters rate candidates into a fixed number of rating
If one and only one candidate is
Unfortunately, if voters cluster in certain categories (e.g. if there are only a handful of ratings, or if ratings are clustered at multiples of 5 or 10), this procedure is likely to end up with multiple candidates reaching a majority at the same rating. Therefore, a tiebreaking procedure is needed. Some possible resolution methods include:
* MCA-A: Most approved candidate (most votes above lowest possible rating). This is also called "Majority Top//Approval", or MTA.
* MCA-P: Most preferred candidate (most votes at highest possible rating).
* MCA-M: Candidate with the highest score at the rating level where an absolute majority first appears
* MCA-S: [[Range voting|Range]] or Score winner.
* MCA-R: Runoff
** MCA-IR
** MCA-AR: Actual runoff: Voters return to the polls to choose one of the finalists. This has the advantage that one candidate is guaranteed to receive the absolute majority of the valid votes in the last round of voting of the system as a whole.
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== Criteria compliances ==
All MCA variants satisfy the [[Plurality criterion]], the [[
All of the methods are [[Summability criterion|summable]] for counting at the precinct level. Only MCA-IR actually requires a matrix (or, possibly two counting rounds), and is thus "[[Summability criterion|summable for k=2]]"
MCA can also satisfy:
* [[Independence of irrelevant alternatives]]
*
* The [[later-no-help criterion]] and the [[Favorite Betrayal criterion]] are satisfied by MCA-P. They're also satisfied by MCA-AR if MCA-P is used to pick the two finalists.
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* MCA-AR satisfies the [[guaranteed majority criterion]], a criterion which can only be satisfied by a multi-round (runoff-based) method.
Thus, the MCA method which satisfies the most criteria is MCA-AR, using [[Schulze]] over the ballots to select one finalist and MCA-P to select the other. Also notable are MCA-M and MCA-P, which, as ''rated'' methods (and thus ones which fail Arrow's ''ranking''-based [[universality criterion]]), are able to seem to "violate [[Arrow's Theorem]]" by
== An example ==
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