Approval does much better than IRV in terms of social utility, the utility of the winner, summed over all the voters, in simulations. A book, _Making Multicandidate Elections More Democratic_, by Samuel Merrill describes Merrill's simulations in more detail. But, by social utility, Approval is clearly better than IRV. IRV's SU problem is what Merrill refers to as the squeeze problem, if I remember his term correctly. The SU maximizing candidate is often eliminated in IRV because of not having as many 1st choice votes as candidates to the sides, in the issue-space. And so IRV then jumps to a low SU extreme. Even if the scenario doesn't start out looking like that, it tends to get that way, if candidates' 1st choice support tapers gradually away from the middle SU maximizing candidate. Then, eliminations start at the extremes, and send transfered votes inward, which pile up on candidates to the sides of the middle candidate. Of course that can cause those candidates to eliminate the middle candidate even if the Middle initially had more votes than anyone. For instance: [Numbers on the left are numbers of voters. The letters after the numbers are the order in which those voters rank candidates. 60: ABCDE 70: BACDE 100: C 83: DECBA 75: EDCBA Not only is C the Condorcet candidate, who'd beat each of the others in pairwise comparisons, and the voter median candidate (it's been shown that, with 1 dimensional issue-space, the voter median candidate is the SU maximizer), but C also is favorite to more voters than any other candidate is. But when the extremes get eliminated, and transfer inward, we find that the candidates to the sides of the voter-median SU maximizer are now big enough to eliminate that candidate. And, as you said, Approval beats IRV not only in SU, but also in not ever giving anyone any incentive to dump their favorite by voting someone else over him/her. With Approval, everyone would always feel free to fully vote for their favorite. That can't be said for Plurality or IRV. Add IRV's nonmonotonicity, its bizarre ability to act oppositely to voters' reaction to new information, and one can only wonder how the CVD IRVies chose to promote IRV. Mike Ossipoff _________________________________________________________________ Send and receive Hotmail on your mobile device: http://mobile.msn.com
