Regarding James C.'s claim that Approval will cause candidates to pander to more voters than IRV will, Roger Myerson undertook a study of how various votiing systems do in that regard.
He proposed an election in which the govt has a certain amount of money to be divided among the voters. Each candidate has his own proposal for how that money is to be divided among the voters. Each candidate makes his offer, his promise to the voters about how he'll divide the money if he wins. It's assumed that people believe him :-) Ok, maybe candidate campain promises are unreliable, but most voters seem to believe them, and so let's disregard that one challengable issue.
He studied a number of voting systems. He found that IRV gives candidates much more incentive to spread their offers thinly & widely, trying to appeal to everyone, as compared to Approval.
That isn't surprising. It costs a lot to get someone's Approval vote. The candidate has to be so good, his offer so great, that the voter is willing to vote him equal to that voter's favorite. Trying to buy more than a few voters therefore wouldn't be feasible. In IRV, it's easier to get support from more voters, since all you need is for them to rank you somewhere reasonably high, or at least not too low. Pander to lots of them, and be something-for-everyone!
But I still like Condorcet best. I don't think Condorcet would cause Nader to pander to Kerry-voter types in order to get them to rank him well. Nader is anything but a panderer. He wouldn't sell himself to the Kerry voters with Condorcet any more than he would with Approval or Plurality.
But Myerson's study shows that IRV gives much more incentive for noncommittal, please-everyone pandering than Approval does.
Check out the article. First, get the _Journal of Economic Perspective_ for Winter '85. It's a special issue on voting systems. It has an article by Robert Weber, entitled "Approval Voting". The references at the end of that article describe a number of interesting, important articles, by Myerson, and by Mylerson & Weber.
One of those articles is about the exstent to which various voting systems give candidates incentive to please everyone. That of course is the one that I'm telling about here. Of course the reference will telll you what issue of what journal that article is in. Maybe someone on this mailing list can tell you directly what journal that is, and which issue of that journal. If not, you can find it via _Journal of Economic Perspective_, as I described.
That references section also has an article by Mylerson about Myerson's corruption test. He compared varioius methods in a model that studied how the methods reward or reject corruption.
In that test model, for simplicity, there's a Yes/No issue on which the various candidates have positions. For a particular voter, a candidate has (dis)utility depending on which position he holds on that Yes/No issue. But, a candidate may also have a nonpositional disutility that's the same for every voter, regardless of that voter's preference on the Yes/No issue. That represents corruption.
Actually, of course, corruption affects issue positions, and so it can't really be separatred from them. But there's stil something to it of value and interest.
The studly showed that Approval will quickly drive corruption from the political system. But that couldn't be said of Plurality. And Borda rewarded and preserved corruption in a way that even Plurailty didn't do. Check out that interesting article.
There's also a reference to an article by Myerson & Weber about a new kind of voting equilibrium that they propose. Put briefly, a Mlyerson-Weber equilibrium is an outcome that doesn't contradict the predictive beliefs that led people to vote in the way that brought about that outcome. Their actual definition is longer than that, but is interesting & elegant. It only applies to "positional" methods such as Approval, Plurality, CR, & Borda.
They show that, with Plurality, almost _any_ two parties can keep being "the 2 only viable parties" at Myerson-Weber equilibrium. The media tell us that they're "The Two Choices", we believe it, we therefore vote for one of them...and guess what: The winner always comes from that pair. Amazing :-)
Mike Ossipoff
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