Hello, Consider these sincere preferences: 49 A>B=C 2? B>C>A 2? C>B>A 100 total
The supporters of B and C, 51% of the voters, agree that A is the worst candidate. But ensuring that the B and C voters can cooperate may be difficult, since B supporters want B to win if possible, and the same is true with the C supporters. In IRV, B supporters might try to communicate to the C voters that they won't give a second preference vote to C. This could happen particularly if B has major party support, and C is just a like-minded independent. The result of this voting behavior might be: 49 A 24 B 27 C>B If, as above, C receives more first preferences than B, B will be eliminated first and A will win. Thus the result of the B supporters' stance may be that C decides it is better not to enter the race at all. Most WV methods fix this situation by electing B, which seems defensible since B receives the most votes of at least some rank. It seems unreasonable to elect A, since a majority vote that B is preferred to A. A problem is that perhaps the B voters are just defecting, in attempt to steal the election from C. With these ballots: 49 A 24 B>C 27 C>B WV methods (as well as IRV) elect C. Thus the addition of the second preference for C, by the B voters, causes B to lose the election. This is a failure of Later-no-Harm, and perhaps being aware of this failure, the B voters defect. C voters could defect, also, concerned about the same problem. If enough B and C voters do this, then A will win. And perhaps in order to avoid this possibility entirely, one of B or C will decide in advance not to enter the race at all. I had thought that IRV's approach (elect A and C respectively in the above scenarios) and WV's approach (elect B and C) were the only approaches possible, but I've noticed another one. In "MinMax (Pairwise Opposition)" or "MMPO," a pairwise matrix is formed as in a Condorcet method, but the winners of pairwise contests are not determined. For each candidate, find how many ballots favored each other candidate over him, and record the largest number. Elect the candidate for whom this number is smallest. This method has flaws: It fails Condorcet, Majority, Plurality, and Clone Independence. But it does satisfy Later-no-Harm. Here is how it handles both of the above scenarios: 49 A, 24 B, 27 C>B or 49 A, 24 B>C, 27 C>B: A: score is 51 (number of B>A voters) B: score is 49 (number of A>B voters) C: score is 49 (number of A>C voters) In other words, a B-C tie, regardless of how many B or C voters defect from the other, so long as over 49 voters rank the same candidate above A. If at least 25 A voters pick a side between B and C, then that would break the tie, also. If a tie still remains, I suggest breaking it with Random Ballot or perhaps FPP, two methods which still satisfy Later-no-Harm. I don't think this would eliminate defections and nomination disincentive, but I think it would go a long way. Any thoughts? Kevin Venzke Découvrez le nouveau Yahoo! Mail : 250 Mo d'espace de stockage pour vos mails ! Créez votre Yahoo! Mail sur http://fr.mail.yahoo.com/ ---- Election-methods mailing list - see http://electorama.com/em for list info