[EM] Re: The Allure of IRV

[Richard Moore]

Dave Ketchum wrote:
> I claim that approval is both weak enough for many of these to notice, 
> and more difficult than its backers are willing to admit:
>      Weak because, if I approve of two candidates, I CANNOT indicate my 
> preference between them.

I cannot buy the notion that this is a real disadvantage. Is being
required to choose between approving one candidate, vs. expressing a
preference for another candidate over that candidate, really an
unacceptable burden to impose on voters? If you believe it is, can you
tell me why?

Preferences that are expressed in Approval tend to be strongly held
preferences, while preferences that are expressed in ranked ballots
are of unknown strength (and sometime negative strength, particularly
in non-Condorcet methods such as IRV and Borda). Thus, the voters may
end up with a CW who is favored by a majority of voters to all other
candidates, but who doesn't have any voters that have a strong
preference for that candidate over their next choice. When the CW and
the AW (Approval Winner) are different, the better choice is probably
the AW, since it is likely that, for the majority that prefer the CW
to the AW (as indicated on rank ballots), that preference is a weak
one -- otherwise that preference would be expressed in the Approval
vote as well. For the minority who approved the AW without approving
the CW, this was more likely to be a strong preference.

Approval does sacrifice individual expressivity in order to gain group
expressivity, but after all when we hold a public election we are
trying to make a social choice, not a private choice.

If it's individual expressivity you want, then Cardinal Ratings are
for you. You'd be perfectly free to sacrifice instrumental voting power
to make a more exact statement about your evaluation of the candidates'
merits.

>      More difficult because where, in the scale between like and 
> dislike, is the point where I should stop approving candidates?

If you are unable to decide whether to approve or disapprove some
candidate, because that candidate is somewhere close to the strategic
borderline between approval and disapproval, then the strategic value
of your vote for that candidate is close to zero (relative to your
strategic values for the high- and low-utility candidates). Therefore
the strategic cost of making the wrong choice on this particular
candidate is very low.

  -- Richard

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