[EM] Myerson's Please-Everyone-Candidate Study

MIKE OSSIPOFF nkklrp at hotmail.com
Sat Nov 20 18:21:48 PST 2004

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 

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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