# Participation criterion

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

## Contents

## Statement of Criterion[edit | edit source]

Adding one or more ballots that vote X over Y should never change the winner from X to Y.

## Variants[edit | edit source]

### Weak Participation criterion[edit | edit source]

By voting, you cannot cause X to be elected instead of Y (with all other winners staying the same) if you scored Y higher than X. One consequence of this criteria, is that by voting, you can never get a result that is less desirable according to your ballot then a result that is more desirable according to your ballot. The difference between this criterion and the strong Strong Participation criterion is that because unless there was an infinite range for you to score candidates on (you are scoring candidates on infinite sliding bars), due to the approximations you make when expressing your utilities on a finite number of scores, your ballot can disagree with you about whether outcome X is better than outcome Y.

(Described here: "Optimal proportional representation" multiwinner voting systems I: methods, algorithms, advantages, and inherent flaws)

### Semi-honest participation criterion[edit | edit source]

This is a weaker form of the participation criterion. It states that for any set of ballots, an extra voter with a given preference set must be able to cast a ballot which is semi-honest and meaningfully expressive, without making the result worse. Meaningfully expressive means that if the voter prefers some set of candidates to the winner, the non-harmful ballot must be able to express that preference.

## Complying Methods[edit | edit source]

This Criteria is important in the context of the Balinski–Young theorem. Failing the participation criterion is an an example of failing Population monotonicity.

Plurality voting, Approval voting, Cardinal Ratings, Borda count, and Woodall's DAC and DSC methods all pass the Participation Criterion. Condorcet methods, Majority Choice Approval, and IRV fail.

All Monroe type Multi-member systems fail participation.

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

## See also[edit | edit source]

- Voting system
- Monotonicity criterion
- Condorcet Criterion
- Generalized Condorcet criterion
- Strategy-Free criterion
- Generalized Strategy-Free criterion
- Strong Defensive Strategy criterion
- Weak Defensive Strategy criterion
- Favorite Betrayal criterion
- Summability criterion

## External links[edit | edit source]

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