Mike, --- MIKE OSSIPOFF <[EMAIL PROTECTED]> a écrit : > I'd said: > > >Consider any standard wv truncation example: > > > >40: A (B>C preference truncated) > >25: B > >35: CB > > > >Maybe you might want to consider your best proposal? > > You replied: > > ...Why on earth would the A voters truncate the B>C preference? > This causes C to obtain a great chance of winning when otherwise it is > a decisive B win. > > I reply: > > Truncation isn't always strategic. Maybe the ballot is very long, and some > people are in a hurry to finish voting and do other things. Maybe someone is > lazy. Maybe someone doesn't know much about some of the candidates. Maybe > someone is refusing, on principle, to vote for someone. > > Those don't sound to me like good reasons to not elect the CW. If someone > refuses to vote for a candidate out of principle, that could make that > candidate lose with any method. No method can always undo the result of not > helping one's best compromise. But wv sometimes can, when the result is a > cycle. WV can still elect the CW under those conditions, and that seems a > good thing. Even though I myself would truncate on prinicple in every > election. > > Besides, what about the people who truncated for those other nonstrategic > reasons. It's good that wv will sometimes not fail to elect the CW as a > result.
I see what you're saying, but as before, it seems to me impossible to elect B (100% of the time) on the above ballots without inviting a defection dilemma. I hope, perhaps unrealistically, that the A voters might list a second preference, since under this method, it cannot hurt A. > I'd said: > > >Your method has a truncation CW failure that PC doesn't have. > > Well, the scenario above shows that if voters truncate the CW, they can > get someone they like less. That isn't your point, I'm sure. > > I reply: > > But if they're truncating for one of those nonstrategic reasons that I > named, then it isn't necessary to teach them a lesson for offensive > strategy, and it's best to elect the CW, as wv will often do, in spite of > truncation, when the Simpson-Kramer version you propose wouldn't. Well, if Random Ballot is then used, then at least the CW has some probability. The point isn't to punish A voters for truncating. The point is to never punish for *not* truncating. > You said: > > I don't understand why you say "halfway" if you're not referring to the > "price" of indecisiveness and poorer Condorcet efficiency. > > I meant that there's a 50% chance of the truncation being regretted in that > defection. But, of course, if it isn't regretted, that's because the CW > wins, and that isn't bad. Are you saying that this method only "halfway" solves the defection problem, because the A voters may regret truncating? Even though they will never regret *not* truncating? > I don't have serious objection to that Simpson-Kramer version. It's largely > a subjective matter of opinion which is better, that or PC. I myself prefer > PC, but I don't strongly object to that Simpson-Kramer version. Ok, I'm pleased to hear that. > You said: > > I don't propose BP in this case because part of the point of CDTT,RB is to > address the defection problem. When only majority-strength defeats are > regarded, then adding a preference can create a defeat, but it can't reverse > the direction of one. That means voters don't need to worry that adding a > new preference could turn that candidate into the CW (who would > automatically > have to win, in a Condorcet method). > > I reply: > > Ok, I hadn't considered new methods or variations, other than ATLO, to get > rid of the defection problem. If CDTT,RB can do so without some high price, > that's desirable. The price is indecision, failing Condorcet and Smith, and failing the Plurality criterion (which, for the scenario at the top, says that C must be elected with no more probability than A). (WV methods except for Raynaud do satisfy Plurality.) > But when the defection succeeds in wv, isn't that in a cycle, rather than > with one candidate beating everyone? Yes. I think you and I look at this situation from different perspectives. You see the B voters as benefiting from defection. I see the B voters as being punished for listing an additional preference. In a Condorcet method, adding a preference for X over Y can only create an obstacle to Y winning if it also removes an obstacle to X winning. So when you add a preference, you have to worry that you might be turning that candidate into the CW, when perhaps a higher preference of yours could have won the cycle- breaker (especially, in a WV method, if your higher preference is expected to get a lot of votes, and thus have stronger wins). So, using MinMax(PO) or a CDTT method, neither the B nor C faction can benefit from defection (in the scenario we were talking about before), period, regardless of what the other faction chooses to do. > You said: > > A big reason I don't mind the indecisiveness, is that the voters have the > power to avoid indecision: They can vote non-cyclic majority-strength wins. > > I reply: > > But indecisiveness would likely adversely affect a method's chance of > acceptance by the public. Yes, that's a shame. But I wonder if it would be worse to elect C with 100% probability in the top scenario; that is an option. > You said: > > Maybe I should note that I want to use Markus' BC with Random Ballot > > You mean the winners, before RB, are the candidates who don't have a > majority beatpath to them that isn't in a cycle of majority defeats? Then > apply RB to the winners? Yes, that's what I mean by "CDTT,RB." I didn't mean this to be new information, but to note that Markus' criterion is more suitable than Steve's. > You continued: > > , because > using Steve's BC is not monotonic. I can give an example if desired. > > I reply: > > Steve mentioned a Beatpath Criterion Method based on BC. If I remember > correctly, it would elect the candidates who could be elected without > violating BC. Then, if (and for as long as) that results in a tie, the same > method would be re-applied to the tie. It was shown to be nonmonotonic. That's interesting; although, even if you don't reapply the method in a tie, and just go to Random Ballot, it's still not monotonic. Suppose pairwise wins A>B>C>A and D>B. D ties with A and C. The potential winners should be {a,c,d}. Now suppose A gets raised on some ballots so that now A beats D pairwise. Then the potential winners are {a,b,c,d}. If these are majority-strength wins, then CDTT,RB elects {d} in the first situation, and {a,b,c,d} in the second, avoiding the monotonicity problem. 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