Truncation

[MIKE OSSIPOFF]

Blake posted an example in which someone can gain by truncation.
No nonprobabilistic method is entirely strategy-free, but we can
reduce the extremeness of defensive strategy need, or the range of
conditions in which drastic defensive strategies are needed. The
defensive strategy criteria show some of the degree of strategy-
freedom that can be gained by the better methods. For instance,
defensive order-reversal is a commonly-needed defensive strategy
in Plurality, IRV, and the margins methods, to an easily avoidable
degree. And those methods have situations in which every Nash equilibrium is 
one in which people use defensive order-reversal.

An outcome that isn't a Nash equilibrium is unstable in a really
obvious way. In Plurality, IRV, and the margins methods, sometimes
the only vote configurations that aren't unstable in that way
are ones in which defensive order-reversal is used.

Maybe margins advocates don't care about strategy problems. They're
in good company: Advocates of Plurality, IRV, and Borda don't either.

But margins advocates need to understand that their standards don't
have some sort of absolute betterness. Let them sell their methods
to people who are as forgiving about strategy problems as they are.
I don't have any argument with them. Their method is great by their
standards.

Blake said:

I think it is possible to penalize partial rankings more severely than
winning-votes does.

I reply:

I wasn't aware that wv penalizes partial rankings. But we've been
all over that issue, and there'd be no point in arguing about it more.

Mike Ossipoff


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