> Date: Sun, 19 Dec 2004 18:56:17 +0100 (CET) > From: Kevin Venzke > Subject: [EM] MMPO, Majority, Condorcet failures
> 29 B > 19 A>B > 9 A>C > 43 C > > CW is C, but the MMPO winner is A. > > This scenario is particularly interesting because A is either > a "weak centrist" candidate, or else someone taking advantage > of the Later-no-help failure. This might be pretty bad. Suppose > the following results are predicted: > > 49 Bush > 24 Gore > 27 Martian candidate > > All the Martian supporters need to do is vote "Martian>Gore" to > ensure a Martian-Gore tie. The only way this can be countered > is by Bush and/or Gore voters having the strategic sense to vote > "Bush>Gore" or "Gore>Bush" (keeping in mind that MMPO satisfies > Later-no-harm, and so can't make their favorite lose). I think that this shows that all voters really should rank all of the candidates, with no equal rankings. In fact, random ranking is better than truncation. Those who think that random ranking is a bad thing won't like this at all. This makes me think of the comparison between MinMax(Winning votes) and MinMax(Margins). Those who think that random ranking susceptibility is a bad thing tend to prefer margins. (Do Later-no-harm compliant methods inherently encourage random ranking?) Those who think that truncation susceptibility is a bad thing tend to prefer winning votes. Personally, I think truncation susceptibility should be avoided more than random ranking susceptibility. On average, random ranking can cause the same problems as truncation. Whereas truncation causes the same change (or non-change, depending on your point of view) in the pairwise contests when each ballot is tallied in turn, random ranking doesn't. There will be slight "perturbations" which are only cancelled out by tallying up more ballots. However, these additional ballots may cause other "perturbations." Therefore, to me I think random ranking is risky. You might as well put down your sincere ranking. Strictly speaking this does not help the voters who have a sincere ranking that are actually truncated rankings. Personally, I would give voting instructions to the voters on the lines of, "It is in your own interest to rank every candidate." In other words, for each candidate, please DECIDE whether the other candidates are better or worse in comparison. Don't sit on the fence. As a result, the sincere rankings would have no tied or truncated rankings. Such rankings may make MMPO more able to handle awkward scenarios. Thanks, Gervase. ---- Election-methods mailing list - see http://electorama.com/em for list info