MIKE OSSIPOFF said: > > Of course that depends on how one defines IIAC. By the simple way that > I define it, Approval & CR comply. But people have told me that they > believe that IIAC means something other than what I say it > means. But no one who has told me that has supplied a complete & > precise definition of what he thinks IIAC means.
I ran across a paper (can't remember the journal, but it was recent) by a mathematician at Northwestern. He defined IIAC to account for strategy changes: If a candidate is deleted, and voters change their strategies to account for that, the outcome should be unchanged unless the deleted candidate was the original winner. Using the maximum-utility strategy causes Approval to flunk this criterion. If you vote for all candidates whom you find superior to an expected utility, deleting a candidate changes the expected utility of the race, which causes you to change strategies, which can change the outcome. I wasn't terribly impressed. First, this definition of IIAC isn't all that useful (any election method flunks it, as far as I can tell). Second, the failure can be proven by a single example, hence the more elaborate aspects of the paper were unnecessary. I know that Donald Saari strongly dislikes Approval Voting. He used to be at Northwestern. My bet is that this guy is from the Saari school of voting theory. Nothing wrong with that (Saari has some fascinating insights) but when a feeble work comes from a group with a known bias, well, it isn't terribly impressive. Incidentally, Saari's problem with Approval seems to be that you can't predict the outcome from knowing the voters' preference orders. This is like saying that you can't predict the outcome of an experiment in one field of physics based on information of an entirely different sort (e.g. magnetic data, fluid dynamics experiment). Alex ---- For more information about this list (subscribe, unsubscribe, FAQ, etc), please see http://www.eskimo.com/~robla/em
