Participation criterion: Difference between revisions
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{{wikipedia}} |
{{wikipedia}} |
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The '''participation criterion''' is a [[voting system criterion]] applicable to both single and multiple winner [[ranked voting system]]s. A method that passes this criterion ensures a voter that it's always better to cast a full honest vote than to not show up for the election at all. It does this by guaranteeing that adding a ballot can never change the winner from someone who is ranked higher on that ballot to someone who is ranked lower. |
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This is the criteria that there is no strategic advantage to not vote. Typically a voter does not know they are in this situation and if they do they can potentially avoid the problem with [[Tactical voting]] |
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While the criterion ensures that a voter can't benefit from staying home rather than voting honestly, a voter may do even better by engaging in [[tactical voting]]; participation does not imply that the method is strategy-proof. |
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== Statement of Criterion == |
== Statement of Criterion == |
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For deterministic single-winner methods, the criterion is defined as follows: |
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the winner from X to Y.}} |
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For multi-winner methods and methods that involve an element of chance, the definition is:<ref name="Woodall-Monotonicity">D R Woodall, [http://www.votingmatters.org.uk/ISSUE6/P4.HTM "Monotonicity and Single-Seat Election Rules"], ''[[Voting matters]]'', Issue 6, 1996</ref> |
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{{definition|The addition of a further ballot should not, for any positive whole number k, reduce the probability that at least one candidate is elected out of the first k candidates listed on that ballot.}} |
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== Variants == |
== Variants == |
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== Complying Methods == |
== Complying Methods == |
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This |
This criterion is important in the context of the [[Balinski–Young theorem]]. Failing the participation criterion is an an example of failing [[Population monotonicity]]. |
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[[Plurality voting]], [[Approval voting]], [[Cardinal Ratings]], [[Borda count]], and Woodall's [[Descending Acquiescing Coalitions|DAC]] and [[Descending Solid Coalitions|DSC]] methods all pass the Participation Criterion. [[Condorcet method | Condorcet methods]], [[Majority Choice Approval]], and [[IRV]] fail. |
[[Plurality voting]], [[Approval voting]], [[Cardinal Ratings]], [[Borda count]], and Woodall's [[Descending Acquiescing Coalitions|DAC]] and [[Descending Solid Coalitions|DSC]] methods all pass the Participation Criterion. [[Condorcet method | Condorcet methods]], [[Majority Choice Approval]], and [[IRV]] fail. |
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All Monroe type |
All Monroe type multi-member systems fail participation. |
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''Some parts of this article are derived with permission from text at http://electionmethods.org'' |
''Some parts of this article are derived with permission from text at http://electionmethods.org'' |
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*[[Favorite Betrayal criterion]] |
*[[Favorite Betrayal criterion]] |
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*[[Summability criterion]] |
*[[Summability criterion]] |
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== References == |
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<references/> |
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== External links == |
== External links == |
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* [http://electionmethods.org/ Election Methods Education and Research Group] |
* [http://electionmethods.org/ Election Methods Education and Research Group] |
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* [http://www.mcdougall.org.uk/VM/ISSUE6/P4.HTM Woodall's DAC method] |
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[[Category:Voting system criteria]] |
[[Category:Voting system criteria]] |