At 09:53 PM 11/7/2006, Chris Benham wrote: >The claim that Range meets IIA (and Clone Independence) rests on the >assumption that the >voters' ratings are "absolute", based on some standard that is >independent of the candidates.
Yes. More accurately, it simply rests on the assumption that voters will not change their vote based on the introduction of a new candidate, with the possible exception of inserting a rank. We assume that in a ranked election, for the purposes of considering IIA, voters will not change their ranks. They might, for example for strategic reasons. But we must assume that they do not do this. The equivalent in a Range election is that voters don't change their ratings. It is only strategic Range voting that would reasonably cause such a change. >According to this assumption, Range doesn't reduce to FPP when there are >two candidates. That's correct. I presume that "reduce to FPP" means that all the other candidates disappear. Since some voters may have expressed weak votes, it can happen that a majority of voters express a weak preference, whereas a minority have expressed strong preference, and thus the choice of the minority prevails. So? (Yes, I agree that there is a kind of problem here, and the problem is intrinsic to Range, but the solution is a ratification vote when there is doubt about the appropriateness of the Range winner due to certain conditions. The problem, though, is much more complex than a simple criterion will address.) >Range promoters like to move the goal posts around. For example one who >has claimed that >Range meets IIA also makes it clear that he expects that voters will >always vote at least candidate >max. and at least one min. One suggested strategy or method of determining votes has been confused, once again, with the method itself. If voters follow that strategy, which does consider candidate space, *as I wrote*, then their ratings will change with the introduction of a new candidate. But this is true of many other methods which are considered to satisfy IIA. However, maybe not. I could not find, easily, any description of what methods satisfy it and what do not, and, it appears, there is some considerable confusion about exactly what this criterion means. I'm assuming that the criterion has an *objective* meaning that does not require information not on the ballot. If it does require such information, then we should know exactly how such information is to be collected. By glossing this over, the problems in application are avoided, and ready assumptions that are not actually true can easily be made. Lack of rigor in definition, I'd say. *As written and with one reasonable interpretation, Range satisfies IIA." You can make other interpretations, especially those that involve internal voter process which is not clearly defined, and then conclude otherwise. ---- election-methods mailing list - see http://electorama.com/em for list info
