Matthew Welland wrote:
So, to re-frame my question. What is the fatal flaw with approval? I'm not interested in subtle flaws that result in imperfect results. I'm interested in flaws that result in big problems such as those we see with plurality and IRV.
IMHO, it is that you need concurrent polling in order to consistently elect a good winner. If you don't have polling and thus don't know where to put the cutoff (between approve and not-approve), you'll face the Burr dilemma: If you prefer A > B > C, if you "approve" both A and B, you might get B instead of A, but if you "approve" only A, you might get C!
Thus the kind of Approval that homes in on a good winner employs feedback. The method is no longer Approval alone, but Approval plus polling. That /can/ work (people approve {Nader, Gore} if Nader has fewer votes than Gore, so that Bush doesn't win from the split, but only approve either Nader or Gore if both are large), but why should we need to be burdened with the feedback?
Some, like Abd, argue that we always reason based on others' positions to know how much we can demand, and so that this is a feature rather than a bug. That doesn't quite sound right to me. In any event, if you want Approval + bargaining (which the feedback resolves to), make that claim. Approval alone, without feedback, will be subject to the flaws mentioned earlier, however.
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