Strategy-free criterion: Difference between revisions
Made a stab at explaining how this criterion relates to strategy.
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(Made a stab at explaining how this criterion relates to strategy.) |
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== Statement of criterion ==
{{definition|If a Condorcet candidate exists, and if a majority prefers this candidate to another candidate, then the other candidate should not win if that majority votes sincerely and no other voter falsifies any preferences.
In a ranked method, it is nearly equivalent to say: {{definition|If more than half of the voters rank ''x'' above ''y'', and there is no candidate ''z'' whom more than half of the voters rank above ''x'', then ''y'' must not be elected.}}
== Complying methods ==
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*'''Complies''': [[Schulze method]] (with winning votes as the measure of defeat strength), [[MDDA]], [[MAMPO]]
*'''Fails''': [[Approval voting]], [[Cardinal Ratings]], [[Borda count]], [[Plurality voting]], [[Instant-Runoff Voting]]
== Intuition ==
By passing the criterion, the method gives a majority who prefers the CW to some other candidate Y the guarantee that if nobody else is reversing their preferences, they (the voters making up the majority) don't need to engage in strategy to prevent Y from being elected. Thus their considerations are "free of strategy" when it comes to preventing Y from being elected, and the minority can't get Y elected by truncation alone.
The actual guarantee is somewhat more complex - see below for the details.
== Commentary ==
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