Steph--
I admit that you've proved that relative margins is better than winning-votes...by your standards. I always point that out in discussions like this. Any method can be the best, depending on what you want. Everyone who values your standards highest should call relative margins the best. The fact that your standards don't address the concerns expressed by voters certainly doesn't mean that your standards are wrong. My defensive strategy criteria measure for the standards of majority rule, and getting rid of the lesser-of-2-evils problem. Those are the concerns that we hear about most from voters and reformers. Other, less widely-shared, standards are valid too, however. If you want to offer a relative margins method as a public proposal, you merely have more work to do, because you'll have to convince people that your standards should be important to them. I want to express my encouragement in that undertaking. But when we talk about the standard of ethics, fairness to the voter, maybe things aren't quite so relativist. Of course the reason why we want a measure of defeat strength is so that we can determine which defeat(s) to drop, or to not keep. When the people have collectively voted in favor of a pairwise defeat, we're tampering with, overruling the expressed public will if we drop that defeat. Overruling a publicly chosen defeat is an undesirable necessity. But at least we can try to minimize the number of people being overruled when doing so. If A pairbeats B, 50 to 40, and if we don't drop that defeat, we're not overruling those 40 people who opposed the defeat. They were overruled in the voting, when they were outvoted, and the people chose to affirm that defeat. So how would we overrule someone? By dropping the defeat. Then we're overruling the public choice, and there are 50 people who have justification to object. So, if fairness to voters is the standard, we want to minimize the number of voters whom we overrule when dropping, or not keeping, a defeat. The people who voted in favor of the defeat are overruled when we drop or skip the defeat. Of course you could say that we should instead look at the sum of all the voters overruled in all the defeats that are dropped. Maybe that requires an as-yet unproposed method, or maybe Ranked-Pairs(wv) already fills the bill. If it requires a new method, one that doesn't meet all the criteria that the wv methods meet, then of course we'd have a choice to make, a familiar situation with voting systems. If the new method were complicated, that would strongly count against it as a public proposal. You wrote: But using ranked pair in this manner brings back Mr. Ossipoff ghost of TRC. I reply: I don't use the Truncation-Resistance Criterion. I defined it almost a decade ago, but it only applies meaningfully to pairwise- count methods. SFC & GSFC apply usefully & meaningfully to all methods, and they generalize TRC. You continue: The fact is Mr. Ossipoff is right: truncating preferences can harm my favourite using margins or relative margins. I reply: No, that isn't what I say. On a topic closest to the one you're talking about, SFC & GSFC say what I say. If you want to limit the discussion to truncation, and pairwise-count methods, then with margins or relative margins, truncation can cause big majority rule violations, and a defensive strategic need to reverse preferences. You continue: But what he does not say is: NOT truncating can harm my favourite using winning votes. So strategy is still an issue, but one we cannot avoid for the moment... I reply: If I led you to believe that wv is entirely strategy-free, then I lied. Gibbard & Satterthwaite showed that no nonprobabilistic method can make that claim. A defensive strategy in wv, the best such strategy, in my opinion, is defensive truncation. In situations where offensive order-reversal is being used against you, then it can succeed if you don't defensively truncate. But in your margins or relative margins, it can succeed if you don't defensively order-reverse. Which situation is worse? I don't claim that wv is completely strategy-free, only that it isn't as strategy-ridden as margins & relative margins. Mike Ossipoff _________________________________________________________________ Chat with friends online, try MSN Messenger: http://messenger.msn.com ---- For more information about this list (subscribe, unsubscribe, FAQ, etc), please see http://www.eskimo.com/~robla/em
