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The participation criterion is a voting system criterion for evaluating voting systems and is also known as the No show paradox. It has been defined as follows:

• Weak participation (Mike Ossipoff): Adding one or more ballots that vote X over Y should never change the winner from X to Y.
• Strong participation (Douglas Woodall): 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.

Plurality voting, approval voting, range voting, and the Borda count all satisfy the participation criterion. All Condorcet methods, Bucklin voting, and IRV fail.

If a voting system fails the participation criterion, then a particularly unusual strategy of not voting can, in at least some circumstances, help a voter's preferred choice win.

The participation criterion for voting systems is one example of a rational participation constraint for social choice mechanisms in general.

Contents 1 Quorum requirements 2 Examples 2.1 Approval voting 2.2 Borda count 2.3 Instant-runoff voting 2.4 Kemeny-Young method 2.5 Minimax Condorcet 2.6 Plurality voting system 2.7 Range voting 2.8 Ranked Pairs 2.9 Two-round system 2.10 Schulze method 3 See also 4 References 5 External links

The most common failure of the participation criterion is not in the use of particular voting systems, but in simple yes or no measures that place quorum requirements. A public referendum, for example, that required majority approval and a certain number of voters to participate in order to pass would fail the participation criterion, as a minority of voters preferring the "no" option could cause the measure to fail by simply not voting rather than voting no. A referendum that required a minimum number of yes votes (not counting no's), by contrast, would pass the participation criterion.

Please help improve this article or section by expanding it. Further information might be found on the talk page or at requests for expansion. (August 2007)

Please help improve this article or section by expanding it. Further information might be found on the talk page or at requests for expansion. (August 2007)

Please help improve this article or section by expanding it. Further information might be found on the talk page or at requests for expansion. (August 2007)

Please help improve this article or section by expanding it. Further information might be found on the talk page or at requests for expansion. (August 2007)

Please help improve this article or section by expanding it. Further information might be found on the talk page or at requests for expansion. (August 2007)

Please help improve this article or section by expanding it. Further information might be found on the talk page or at requests for expansion. (August 2007)

Please help improve this article or section by expanding it. Further information might be found on the talk page or at requests for expansion. (August 2007)

Please help improve this article or section by expanding it. Further information might be found on the talk page or at requests for expansion. (August 2007)

Please help improve this article or section by expanding it. Further information might be found on the talk page or at requests for expansion. (August 2007)

Please help improve this article or section by expanding it. Further information might be found on the talk page or at requests for expansion. (August 2007)

• Consistency criterion
• Voting system

• Woodall, Douglas R, "Monotonicity and Single-Seat Election Rules" Voting matters, Issue 6, 1996.

Some parts of this article are derived with permission from text at http://electionmethods.org

• Traditional single-winner criteria by Mike Ossipoff
• Electoral criteria by Blake Cretney
• Voting criteria by James Green-Armytage
• A Strong No Show paradox is a common flaw in Condorcet voting correspondences by Joaquin Perez.