Majority Defeat Disqualification Approval: Difference between revisions

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'''Majority Defeat Disqualification Approval''' or '''MDDA''' is a method devised by Kevin Venzke for the purpose of showing that the [[Favorite Betrayal criterion]], [[Strategy-Free criterion]], and [[Strong Defensive Strategy criterion]] are mutually compatible. The name was given by Mike Ossipoff.
 
'''Majority Defeat Disqualification Approval''' or '''MDDA''' is a method devised by Kevin Venzke for the purpose of showing that the [[Favorite Betrayal criterion]], [[Strategy-Free criterion]], and [[Strong Defensive Strategy criterion]] are mutually compatible. The name was given by Mike Ossipoff.
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This method can be viewed as a variant of [[Improved Condorcet Approval]].
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Another method with the above properties is [[Majority Approval, Minimum Pairwise Opposition]] ([[MAMPO]]).
   
 
==Procedure==
 
==Procedure==
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A candidate is ''dominated'' if more than half of the voters rank some other candidate strictly above him.
 
A candidate is ''dominated'' if more than half of the voters rank some other candidate strictly above him.
   
Sort the candidates so that all undominated candidates, if any exist, come before all dominated candidates. Within each group, sort of the candidates in descending order of approval.
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All dominated candidates are eliminated, unless this would eliminate all the candidates.
   
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Of remaining candidates, the one approved by the most voters is elected.
Elect the first candidate in the resulting ranking.
 
   
 
==Criteria==
 
==Criteria==
'''MDDA''' satisfies the [[Favorite Betrayal criterion]], [[Strategy-Free criterion]], the [[Strong Defensive Strategy criterion]] (and [[Minimal Defense criterion]]), [[Monotonicity criterion|monotonicity]], and (''check this'') the [[Plurality criterion]].
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'''MDDA''' satisfies the [[Favorite Betrayal criterion]], [[Strategy-Free criterion]], the [[Strong Defensive Strategy criterion]] (and [[Minimal Defense criterion]]), and [[Monotonicity criterion|monotonicity]].
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It fails [[Strategic nomination|Clone-Winner]], the [[Plurality criterion]], the [[Generalized Strategy-Free criterion]], the [[Condorcet criterion]], the [[Smith set|Smith criterion]], [[Participation criterion|Participation]], the [[Majority criterion|Majority criterion for solid coalitions]], and [[Later-no-harm criterion|Later-no-harm]].
   
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==Links==
It fails [[Strategic nomination|Clone-Winner]], the [[Generalized Strategy-Free criterion]], the [[Condorcet criterion]], the [[Smith set|Smith criterion]], [[Participation criterion|Participation]], the [[Majority criterion|Majority criterion for solid coalitions]], and [[Later-no-harm criterion|Later-no-harm]].
 
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*[http://lists.electorama.com/pipermail/election-methods-electorama.com/2005-June/016374.html Method is first proposed on EM, with properties proven (Jun 21 2005)]
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*[http://lists.electorama.com/pipermail/election-methods-electorama.com/2005-June/016381.html Mike Ossipoff names the method]
   
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[[Category:Single-winner voting methods]]
''Work in progress.''
 
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[[Category:Ranked voting methods]]
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[[Category:Monotonic electoral systems]]

Revision as of 10:51, 29 June 2022

Majority Defeat Disqualification Approval or MDDA is a method devised by Kevin Venzke for the purpose of showing that the Favorite Betrayal criterion, Strategy-Free criterion, and Strong Defensive Strategy criterion are mutually compatible. The name was given by Mike Ossipoff.

This method can be viewed as a variant of Improved Condorcet Approval.

Another method with the above properties is Majority Approval, Minimum Pairwise Opposition (MAMPO).

Procedure

The voter submits a ranking of the candidates. The candidates explicitly ranked are considered approved by that voter.

A candidate is dominated if more than half of the voters rank some other candidate strictly above him.

All dominated candidates are eliminated, unless this would eliminate all the candidates.

Of remaining candidates, the one approved by the most voters is elected.

Criteria

MDDA satisfies the Favorite Betrayal criterion, Strategy-Free criterion, the Strong Defensive Strategy criterion (and Minimal Defense criterion), and monotonicity.

It fails Clone-Winner, the Plurality criterion, the Generalized Strategy-Free criterion, the Condorcet criterion, the Smith criterion, Participation, the Majority criterion for solid coalitions, and Later-no-harm.

Links