[EM] serious strategy problem in Condorcet, but not in IRV?

[James Green-Armytage]

>James, 
>your own example 
>Sincere preferences
>46: A>B
>44: B>A
>5: C>A
>5: C>B
>shows a typical FPTP informational strategy opportunity. 
>You should inform Mr. Monroe about it... 
>It comes from the fact that FPTP forces C>B voters to choose 
>between C>A=B  or A>C=B (using universal ballots syntax). 
>You cannot assume the degree of information voters have to make their
>decision, 
>it is a part of the strategical problems. Mr. Monroe sets this aside when
>he makes his 
>analysis... 


Stephane,

Please keep in mind that I am not really presenting Monroe's argument, but
rather a somewhat bastardized interpretation thereof. However, Monroe
isn't saying that IRV and plurality don't present strategy incentives. I
think that that is obviously wrong. (Also, I doubt that Mike Ossipoff and
Russ Paielli would have made such a statement, because on their web site
they show plurality as failing numerous strategy criteria.) It is a
particular kind of strategy that Monroe is concerned with, and one which
he finds more disturbing than the kind of strategy you illustrate above.

The problem with plurality (and to a lesser extent, with IRV, though not
in this example) is that the C voters are forced to choose between a
sincere vote and the lesser of two evils. In the terminology stated by
Markus in a recent posting, this is the "compromising" strategy. 

I agree that it is a very serious problem to force voters to make this
kind of compromising choices on a regular basis, as plurality clearly
does. But what Monroe is concerned with is more so the "burying" strategy,
and its possible consequences. In this particular example, what would
worry him (I think) is that A and B voters will both try to get a bury
each other, and will inadvertently elect C as a result, which I agree
would be a public disaster.

James