CDTT: Difference between revisions

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== Uses ==
 
Limiting an election method's selection to the CDTT members can permit it to satisfy the [[Minimal Defense criterion]] (and thus the [[Strong Defensive Strategy criterion]]) and the [[Mutual majority criterion|Majority criterion for solid coalitions]], while coming close to satisfying the [[Later-no-harm criterion]]. Specifically, the CDTT completely satisfies [[Later-no-harm criterion|Later-no-harm]] in the three-candidate case, and failures can only occur in the general case when there are majority-strength cycles.
 
(Please see the articles on the [[Minimal Defense criterion]] and [[Later-no-harm criterion]] for commentary on the significance of these criteria.)
In order to maximize Later-no-harm compliance, the CDTT should be paired with a method that itself fully satisfies Later-no-harm. In order to ensure that [[Monotonicity criterion|Mono-raise]] is not failed, the paired method should be used to generate a ranking of the candidates which is not influenced by which candidates make it into the CDTT. Then the CDTT member who appears first in this ranking is elected.
 
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Some methods which can be paired in this way with the CDTT:
*'''[[Random Ballot]]''': This can be very indecisive, but it is conceptually simple, and it satisfies [[Monotonicity criterion|Mono-raise]] and Clone Independence.
*'''[[Plurality voting|First-Preference Plurality]]''': This is decisive, simple, and [[Monotonicity criterion|monotone]], but fails Clone Independence.
*'''[[Instant-runoff voting|Instant Runoff Voting]]''': This is more complicated. It satisfies Clone Independence but not [[Monotonicity criterion|monotonicity]]. The IRV ranking would be the reverse of the candidates' elimination order.
*'''[[Descending Solid Coalitions]]''': This is also somewhat complicated, but it's the only non-random option which satisfies Clone Independence and [[Monotonicity criterion|Mono-raise]].
*'''[[Minmax|MinMax (Pairwise Opposition)]]''': This has the advantage that it is calculated based on the pairwise matrix, just as the CDTT itself is. However, it is somewhat indecisive and fails Clone Independence. It satisfies [[Monotonicity criterion|Mono-raise]].
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