Markus said: in so far as IRV meets majority for solid coalitions and independence from clones, IRV can hardly be called "erratic" compared to primary with runoff. I reply: If I tell you that someone drives erratically, that fortunately doesn't mean that he does everything that can be called erratic. IRV is erratic because it requires strict ordering, collects a ranking, and then makes irreversable decisions based only on a fraction of the ballots' information, looking only at 1st choice votes. But it was inevitable that eventually someone would post about IRV's criterion successes. When Markus says "majority for solid coalitions", I assume that he means what I call Mutual Majority, and Bruce Anderson used to call Generalized Majority Criterion. I renamed it Mutual Majority because I didn't find it to be very general. It's about a fortuitous special case. Here's Mutual Majority, written in a way that's contrived so that Approval won't pass: If there's a group of voters who are a majority of all the voters and who all prefer all the candidates in a certain set to all the candidates outside that set, and if those voters vote sincerely, then the winner should come from that set of candidates. [end of definition] Sounds good, but a mutual majority is also a situation where IRV will demonstrate its failures of FBC & WDSC, showing its lesser-of-2-evils problem and its gross and avoidable violation of majority rule. Say you believe, rightly or wrongly, that there's a majority who prefer both Worst & Middle to Favorite. Why should you vote Favorite in 1st place? No reason to. He can't win. But you can gain by voting Middle in 1st place, in case he needs your vote to avoid immediate elimination and the subsequent transfer of his votes to Worst. The Clone Criterion, too, is about a special case. Sure, with IRV, adding clones won't hurt your faction, but other ordinary & typical situations will make IRV violate FBC & WDSC. WDSC says: If a majority of all the voters prefer A to B, then they should have a way of voting that ensures that B won't win, without any of them reversing a sincere preference. [end of definition] Approval passes FBC & WDSC. Plurality & IRV fail both. Mike Ossipoff _________________________________________________________________ Chat with friends online, try MSN Messenger: http://messenger.msn.com
