Voting system criterion

A formally defined pass/fail criterion by which a voting system may be assessed.

Though a voting method may pass or fail a given criterion, that does not mean the voting method can't almost always pass or fail the criterion in practice, or that when it passes or fails the criterion, that this will be particularly bad. Advocates of various voting methods often make the argument that though their method may fail some criteria, that this should not be considered a major drawback of their methods; for example, advocates of Approval voting and IRV often argue that though those methods fail the Condorcet criterion, they almost always meet it in practice, and that when they fail it, it is for good reason, or at least not particularly bad.

Many criteria relate to sets of candidates; see the set theory article for more information.

Examples for such criteria are:

• Condorcet criterion, Consensus Criteria, Consistency criterion, Favorite Betrayal criterion, Generalized Strategy-Free criterion, Greatest Possible Consensus Criterion, independence from irrelevant alternatives, local independence from irrelevant alternatives, invulnerability to burying, invulnerability to compromising, Later-no-harm criterion, Monotonicity criterion, Pareto criterion, Participation criterion, Plurality criterion, Schwartz criterion, Smith criterion (also known as Generalized Condorcet criterion), Independence of clones, Strategy-Free criterion, Strong Defensive Strategy criterion, Summability criterion, Unanimous Consensus Criterion, Weak Defensive Strategy criterion

Absolute criterion

An absolute criterion requires or prohibits some result due to some characteristic of a given a set of ballots. This is in contrast to the below-mentioned relative criterion, which requires (or prohibits) a change in the election's result given some modification to the ballots.

Examples of absolute criteria

• Condorcet criterion, Smith criterion, Plurality criterion, Minimal Defense criterion, Majority criterion, Pareto criterion

Relative criterion

A relative criterion requires that when the ballots are changed in some way, the result of the election must or must not change in some way. This is in contrast to the above-mentioned absolute criterion, which requires some result given some characteristic of a set of ballots.

Examples of relative criteria

• Monotonicity criterion, Participation criterion, Later-no-harm criterion, Later-no-help criterion, Sincere Favorite criterion, Independence of irrelevant alternatives, Independence of clones, Neutrality of Spoiled Ballots

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