[EM] Unranked-IRV, Cumulative, and Normalized Ratings

Forest Simmons fsimmons at pcc.edu
Thu Apr 19 18:12:05 PDT 2001

This is more of a query about Lori Cranor's method than anything else.

If it really gives no strategic incentive for distorting ratings, it
sounds like the ideal way to use CR ballots.

Here's what puzzles me. On the one hand, it seems like any method like Ms
Cranor's that uses CR ballots to formulate optimal Approval Strategies
should be able to do so in a way that would give the win to the candidate
with the greatest average rating.

If that is the case, then it seems like any strategy that would improve
the average rating of your favorite on the CR ballot would be tempting. In
other words, one would be tempted to distort ratings. 

On the other hand, if the method doesn't give the win to a maximally rated
candidate, then it probably isn't much better than plain old Approval in
social utility.

Can you shed any light on this?


On Tue, 10 Apr 2001, Richard Moore wrote:

> Martin Harper wrote:
> > Richard Moore wrote:
> >
> > > ...unless the voters let the system do the strategizing for them.
> > >
> > >
> > > [snip]
> > >
> > >
> > > would the voters have any reason to give insincere ratings
> > > (assuming they understand and trust the system)?
> >
> > They might want to give insincere ratings to try and distort the strategies of
> > their co-voters, in the same way that (say) in Approval polls you reduce your
> > willingness to compromise. The fact that you have to make the same vote in the
> > 'poll' as in the final vote reduces such options, though - which'd make it harder
> > to do - but not impossible.
> I thought of the possibility of distorting the opposing strategies, but to do this
> you have to fool the method's predictor, and to get to the predictor you have
> to go through the strategizer first. You can't fool the predictor without fooling
> the strategizer, and if you fool the strategizer you wreck your own strategy. So
> I suspect it might not just be harder, it might be impossible.
> > > convergence
> >
> > Isn't there a theorem in game theory which says that all games must have at least
> > one attractor? Does this apply to the 'game' of voting, which'd show that we'd
> > always get convergence?
> I don't have the answers to these questions. There may be such a theorem but
> I'm not familiar with it. But I don't believe that the presence of an attractor
> guarantees convergence. The attractor might only force the system into a stable
> orbit. And if there are multiple attractors?
> Richard

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