2010/6/23 Kevin Venzke <[email protected]> > Hi Jameson, > > --- En date de : Mer 23.6.10, Jameson Quinn <[email protected]> a > écrit : > >3a. Quasi-elimination. I believe that winning-votes Condorcet methods, > >like Schulze, are an attempt to ensure that A wins even in the face of > >B's truncation. However, this only works if C voters truncate rather than > >splitting evenly between CBA and CAB. Other stronger quasi-elimination > >systems that I know of have IRV-like problems. > > I would say that WV methods attempt to ensure that {A,B} wins even in > the face of B's truncation. Making A win despite truncation will often be > impossible without violating Plurality (e.g. with MMPO). > > >4. Runoff. Viewed in an outcome-oriented game-theoretic vacuum, this is > >just the same as elimination, and it suffers the same problems. However, > >if voters have some negative utility for the runoff itself, then a system > >can use the threat of one to motivate honest voting in the first round. > >Since the scenario assumes that there is a clear winner with no cycles > >under honest voting, that may be enough. > > I see the use of leaving no purpose for insincerity in the second round. > For example supporters of candidate C may find it too risky to give a > second preference to one of the opposing clones, but once C has been > removed from consideration, there's no more disincentive. > > It's not quite clear to me how to use a runoff to ensure sincerity in > the first round, in general. >
I am not saying that a runoff "threat" can ensure sincerity in the first round in general. I am only speaking of this one scenario. If I were to generalize, I think that runoffs can help prevent insincere Condorcet cycles, but can do nothing about real ones. I think that's enough, because I suspect that insincere ones are more common. Incidentally, any runoff methods which works for this purpose would eliminate one of the clones (probably B) and leave A facing C, not B, in the runoff. Methods which eliminate C depend on cooperation from A and B - and thus eliminate A when B doesn't cooperate, which defeats the purpose. JQ
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