[EM] Fluffy the Dog and group strategy

[Craig Layton]

Hi all,

I'm comming in a little late, but I just wanted to clarify one or two things
in relation to the fluffy
example.  I don't believe that it invalidates Condorcet methods, which I
still nominally support.  It was written a while ago and I guess it
represents me comming to terms with the low utility condorcet winner
argument.  I have also argued against most of the alternatives to Condorcet
(except for the Dyadic Approval and Universal Approval methods, which I'm
still contemplating) so perhaps I'm just a negative fellow :-)

I think Dave Ketchum argued that the fact that the majority of voters prefer
fluffy to either candidate and they have voted thus means that there isn't
anything objectionable about the result.  The problem with this kind of
statement is that it sounds like a re-statement of the Condorcet criterion,
which amounts to the argument; "the Condorcet criterion is a good idea
because the Condorcet criterion is a good idea".

This kind of example also brings up a game-theoretic type argument about the
voters' best course of action.  It has been argued in the past that when
there is a Condorcet winner, a sincere vote is always the best strategic
vote.  From an individual agent's point of view, sitting in the polling
booth, working out how to vote, this is indeed the case.  However, the
supporters of the other two candidates (not fluffy) would be best served by
getting together before-hand and working out some kind of deal, probably a
simple agreement to truncate (only vote 1 for their favourite candidate).
Deals between factions are possible in almost every type of voting system -
except for systems like plurality, at least to the extent that it isn't
possible for two groups of voters to increase both of their chances of
winning and/or their expected utiltiy outcomes.

The difference in the low condorcet winner scenario is that the deal is
low-risk.  Given that each of the main factions don't have a very strong
preference between the other two candidates, they don't have much to lose
and the free-rider effect is minimalised.  Now that I think about it, it is
actually highly likely that many voters will naturally vote this way anyway
(truncate a ballot if there is no significant difference between the rest of
the candidates), so perhaps it isn't as much of a problem for Condorcet as I
originally imagined.

I might write more about group strategy later.  It is a real problem in
preferential systems, and maybe a potential problem in methods like
approval.

Craig