Voting system criterion: Difference between revisions
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Some criteria are very widely agreed to be important. Examples: |
Some criteria are very widely agreed to be important. Examples: |
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* [[Pareto]]: If everybody prefers X to Y, then the method's ranking should also prefer X to Y. |
* [[Pareto]]: If everybody prefers X to Y, then the method's ranking should also prefer X to Y. |
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* Anonymity/Fairness: All candidates and voters should be treated identically. |
* Anonymity/Fairness: All candidates and voters should be treated identically. |
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* [[Participation criterion]]: Showing up to vote shouldn't make a candidate you prefer lose. |
* [[Participation criterion]]: Showing up to vote shouldn't make a candidate you prefer lose. |
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* [[Summability criterion]]: All the data the method uses to call the election should be expressible as a short summary. |
* [[Summability criterion]]: All the data the method uses to call the election should be expressible as a short summary. |
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Sometimes desirable properties or criteria are called desiderata. |
Sometimes desirable properties or criteria are called desiderata. |
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Here are some criteria often touted by advocates of [[majority rule]], split into categories of "widely agreed on" and criteria which are more polarizing: |
Here are some criteria often touted by advocates of [[majority rule]], split into categories of "widely agreed on" and criteria which are more polarizing: |
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[[Majority criterion]], [[Mutual majority criterion]], [[Majority loser criterion]], [[Droop proportionality criterion]] |
[[Majority criterion]], [[Mutual majority criterion]], [[Majority loser criterion]], [[Droop proportionality criterion]], [[Condorcet criterion]], [[Smith criterion]], [[Condorcet loser]] |
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[[Condorcet criterion]], [[Smith criterion]], [[Condorcet loser]] |
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=== Proportionality-related criteria === |
=== Proportionality-related criteria === |
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[[Proportionality for Solid Coalitions]] |
[[Proportionality for Solid Coalitions]], [[Justified representation]], [[Perfect representation]], [[Stable Winner Set]], [[Quota rule]] |
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[[Justified representation]] |
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[[Perfect representation]] |
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[[Stable Winner Set]] |
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[[Quota rule]] |
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=== Strategic voting-related criteria === |
=== Strategic voting-related criteria === |
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These generally are considered essential and basic features of any voting method |
These generally are considered essential and basic features of any voting method |
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[[Discrimination axiom]], [[Homogeneity criterion]], [[Scale invariance]] |
[[Discrimination axiom]], [[Homogeneity criterion]], [[Scale invariance]], [[Anonymity criterion]], [[Neutrality criterion]] |
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=== Miscellaneous criteria === |
=== Miscellaneous criteria === |
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*[[Monotonicity criterion]], [[Participation criterion]], [[Later-no-harm criterion]], [[Later-no-help criterion]], [[Sincere Favorite criterion]], [[Independence of irrelevant alternatives]], [[Strategic nomination|Independence of clones]], [[Neutrality of Spoiled Ballots]], [[Reversal symmetry]] |
*[[Monotonicity criterion]], [[Participation criterion]], [[Later-no-harm criterion]], [[Later-no-help criterion]], [[Sincere Favorite criterion]], [[Independence of irrelevant alternatives]], [[Strategic nomination|Independence of clones]], [[Neutrality of Spoiled Ballots]], [[Reversal symmetry]] |
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== Other systems == |
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===Consensus criterion=== |
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[[Consensus criteria]] attempt to guarantee the election of consensus candidates. Examples of such criteria include [[greatest possible consensus criterion]] and [[unanimous consensus criterion]]. |
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== Notes == |
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=== Proportional Representation === |
=== Proportional Representation === |
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[[Proportional representation]] is the general idea that groups of voters with shared preferences should be able to win an amount of representation in a multi-winner body (a legislature) proportional to how large they are. In partisan PR methods, proportionality can be measured using various measures of how well a party's seats matched up to its share of votes. For nonpartisan methods, there is disagreement on how to measure or quantify PR. |
[[Proportional representation]] is the general idea that groups of voters with shared preferences should be able to win an amount of representation in a multi-winner body (a legislature) proportional to how large they are. In partisan PR methods, proportionality can be measured using various measures of how well a party's seats matched up to its share of votes. For nonpartisan methods, there is disagreement on how to measure or quantify PR. STV advocates typically request only [[Proportionality for Solid Coalitions]], which is meant to account for coherent factions that can be identified from the rankings. |
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=== Rated ballot adaptations === |
=== Rated ballot adaptations === |
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Several criteria have rated-ballot or other adaptations that may make more sense in certain contexts. For example, the [[majority criterion]] says that a candidate preferred by a majority over all other candidates must win. The [[Majority criterion for rated ballots]] further requires the majority to give this candidate the highest score. It can be argued that a voter who gives their favorite candidate less than full support (i.e. didn't do [[normalization]]) doesn't deserve full power, so this modification to the criterion ensures that only a strategic or strongly supportive majority gets their way. Similar adaptations can be made to any criterion involving voter preferences determining who should win, such as [[PSC]], the [[plurality criterion]], [[ |
Several criteria have rated-ballot or other adaptations that may make more sense in certain contexts. For example, the [[majority criterion]] says that a candidate preferred by a majority over all other candidates must win. The [[Majority criterion for rated ballots]] further requires the majority to give this candidate the highest score. It can be argued that a voter who gives their favorite candidate less than full support (i.e. didn't do [[normalization]]) doesn't deserve full power, so this modification to the criterion ensures that only a strategic or strongly supportive majority gets their way. Similar adaptations can be made to any criterion involving voter preferences determining who should win, such as [[PSC]], the [[plurality criterion]], [[mutual majority]], etc. |
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== References == |
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[[Category:Voting system criteria|*]] |
[[Category:Voting system criteria|*]] |
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[[Category:Voter strategy]] |
[[Category:Voter strategy]] |
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{{fromwikipedia}} |
<references />{{fromwikipedia}} |