Difference between revisions of "Strategy-free criterion"

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<h4 class=left>= Definitions</h4> ==
<p>A [[sincere vote]] is one with no falsified preferences or preferences left unspecified when the election method allows them to be specified (in addition to the preferences already specified).</p>
<p>One candidate is preferred over another candidate if, in a one-on-one competition, more voters prefer the first candidate than prefer the other candidate.</p>
<p>If one candidate is preferred over each of the other candidates, that candidate is called "Condorcet candidate" or "Condorcet winner".</p>
<h4 class=left>= Statement of Criterion</h4> ==
<p><em>''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.</em></p>''
<h4 class=left>= Complying Methods</h4> ==
[[Category:Voting system criteria]]
<h4 class=left>Complying Methods</h4>
*'''Complies''': [[Cloneproof Schwartz Sequential Dropping]]
<p>[[Cloneproof Schwartz Sequential Dropping]] complies with the Strategy-Free Criterion, while*'''Fails''': [[Approval voting]], [[Cardinal Ratings]], [[Borda count]], [[Plurality voting]], and [[Instant-Runoff Voting]] do not comply.</p>
<h4 class=left>= Commentary</h4> ==
<p>The reader may be wondering how the Condorcet candidate, if one exists, could
possibly <em>not</em> be preferred by a majority of voters over any
other candidate. The key is that some voters may have no preference
prefer the opposite, with the other 15 having no preference between the
two. In that case, it is not true that a majority of voters prefer the
Condorcet candidate over the other candidate, and SFC does not apply.</p>
<p>In order to understand SFC, one must also understand that there are
two types of insincere votes: false preferences and truncated
preferences. Voters <em>truncate</em> by terminating their rank list
voter's true preferences are (A,B,C,D). The vote (A) or (A,B) would be a
truncated vote, and the vote (B,A,C) or (A,C,B) would be a falsified
<p>SFC requires that the majority of voters who prefer the Condorcet candidate to
another particular candidate vote sincerely (neither falsify nor
truncate their preferences), and it also requires that no other voter
that is more likely to backfire than to succeed.) The significance of
the SFC guarantee is that the majority has no need for defensive
strategy, hence the name Strategy-Free Criterion.</p>
<p>[[Cloneproof Schwartz Sequential Dropping]] was shown to comply with both the
Condorcet and Generalized Condorcet Criteria (CC and GCC) above.
Although compliance with CC and GCC are important, those criteria apply
reasonable conditions, a majority of voters have no incentive to vote
insincerely. The fact that [[Cloneproof Schwartz Sequential Dropping]] also complies with SFC
therefore enhances the significance of CC and GCC considerably.</p>
''Some parts of this article are derived with permission from text at http://electionmethods.org''
== See Also ==
*[[Voting system]]
*[[Monotonicity criterion]]
*[[Condorcet Criterion]]
*[[Generalized Condorcet criterion]]
*[[Generalized Strategy-Free criterion]]
*[[Strong Defensive Strategy criterion]]
*[[Weak Defensive Strategy criterion]]
*[[Favorite Betrayal criterion]]
*[[Participation criterion]]
*[[Summability criterion]]
== External Links ==
* [http://electionmethods.org/ Election Methods Education and Research Group]
[[Category:Voting system criteria]]
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