Participation criterion

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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, majority choice approval, 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.

1 Quorum requirements
2 See also
3 References
4 External links

[edit] Quorum requirements

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.