Condorcet method: Difference between revisions

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* [B] indicates voters who preferred the candidate listed in the row caption to the candidate listed in the column caption
 
In this election, Nashville is the Condorcet winner (Nashville beats Memphis 58 to 42, and Chattanooga and Knoxville 68 to 32) and thus the winner under all possible Condorcet methods.
 
== Connection to cardinal methods ==
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Score Voting can be thought of as a Condorcet method where a voter is allowed to give a fraction of a vote to a candidate in a pairwise matchup against other candidates, rather than a full vote or nothing. Assuming a voter would vote the exact same way in a Score Voting runoff between all possible pairs of candidates as they did in the original Score election, Score elects the Condorcet winner using this modified definition.<ref>https://rangevoting.org/CondDQ.html</ref>
 
It's possible to modify Score to be more like a traditional Condorcet method by allowing voters to write the scores they would give to every possible pair of candidates in a Score runoff, and then using a Condorcet method to process this, treating a score of, say, A5 B3 (where the max score is 5) as 0.4 votes for A>B. As this would be utterly infeasible with just a few candidates running however, one way to accomplish most of the same objective is to allow voters to mark on their ballots that they want their vote strategically optimized, meaning that if their cardinally expressed preferences are A5 B3 Z2, instead of having their vote considered as B3 Z2 in an B vs. Z runoff, it would be considered as B5 Z0 (if the max score is 5), which is functionally equivalent to the Plurality voting runoffs that are used for the traditional Condorcet winner definition. This strategic optimization can be done fractionally to allow a voter to customize how much optimization they want to be done with their scores in each runoff. It is also possible for voters to indicate an approval threshold, meaning that for all approved candidates, no strategic optimization is applied to pairwise matchups between them, but all pairwise matchups between approved and disapproved candidates are strategically optimized. With this modification, if all voters use strategic optimization, Score becomes a traditional Condorcet method (which will need a cycle resolution method to be applied at times), but if no voters strategically optimize, it remains Score (which never needs cycle resolution methods to be applied).
 
Note that the above schemes can make Score fail the logical property that a voter's strength of preference between any pair of candidates must equal the sum of the strengths of preference between all sequential pairs of candidates in a beatpath from the first candidate of the pair to the second. The failure of this property seems to be the major reason traditional Condorcet methods can have Condorcet cycles and one major reason for why they fail certain properties such as Favorite Betrayal and Independence of Irrelevant Alternatives.
 
== Demonstrating pairwise counting ==
Condorcet winners and the Smith Set in general are often the equilibrium outcomes of iterated voting methods. The CW in particular is the Nash Equilibrium of Score Voting. Here are demonstrations of equilibrium convergence using Asset Voting:
 
 
https://preview.redd.it/12xydzctoh441.png?width=1556&format=png&auto=webp&s=75a8c62cac30f1c6a22102974b3ed520c2f3c5b2
 
https://preview.redd.it/b2d38idknh441.png?width=1556&format=png&auto=webp&s=b5ddfb5dffa1098f0c5f2e995c3d67a9ecddb424
 
== Use of Condorcet voting ==