[EM] Strategic voting in ratings

[Roy]

Richard Moore <rmoore4 at h...> wrote:
> 	deltaEU = X*( 100*deltaPa + 50*deltaPb )
> ...
> Consider that if
> 100*deltaPa + 50*deltaPb is positive, you will get a
> positive strategic benefit ...
> maximized if X is set to the full-scale positive 
> rating. On the other hand, if the value in parentheses is 
> negative, ...you would want to minimize the negative impact by 
> voting B at the lowest end of the scale.

So we'd have to know deltaPa and deltaPb to know how to vote 
strategically, or at least know whether the magnitude of dPb is > 
twice dPa. I presume that if dPb = -2dPa, we vote sincerely.

Strategic voting (at least, among non-statisticians) is based on a 
perceived runoff: a sense that the race is really between (or among) 
a subset of the candidates. When voters have that perception, they 
will normalize their votes for those who are. Granted. I don't think 
that necessitates degenerating completely to Approval. Those who 
aren't considered in the race would still be voted sincerely (to 
scale).

Your example seems to ignore deltaPc, which has positive utility to 
the voter. Is that because the support for C is zero? I'm not sure 
that multiplication can properly be applied to utility. Is a utility 
of 1 really infinitely more -- um, utilitous than a utility of zero? 
Of course, I'm one of those non-statisticians I spoke of.

The other thing your example ignores is group dynamics: when a lot of 
people are in the same situation, they will have similar decisions to 
make, and a lot of them will choose similarly. Hence, the linearity 
in X is questionable, because the population might effectively be 
made small by a lot of people acting as one. (cf Goedel, Escher, Bach)