[EM] Fwd: Is Condorcet The Turkey?

[Bart Ingles]

Dave Ketchum wrote:
>
> Bart Ingles wrote:
> > (2)  The people I have talked to on this list and elsewhere who have
> > actually been involved in conducting elections have been pretty adamant
> > that the system must be simple to administer, participate in, and
> > understand.
> 
> I claim Condorcet fits.  Fact that people cannot do the recording both
> fast and correctly does not make understanding how it is done that difficult.

The recording is simple to explain but not feasible to do manually. 
Using the matrix to determine the actual winner is doable manually but
more difficult to explain to the general public.


> > (4)  One Condorcet strategy situation occurs to me which apparently
> > does not involve a prisoner's dilemma: when you really do have NO
> > preference between some of the candidates.  In this case, it seems to
> > me, you should always rank the indifferent candidates strategically
> > relative to one another, presumably by burying the one(s) who present
> > the greatest threat to your favorite.
> 
> By listing your favorite first you have already said as much as you can to
> protect your favorite.  If you like/dislike this collection equally you
> reasonably list them together, but the only reason to do this sublist
> other than randomly would be because you DO care which of them wins if
> they become part of the decision.

Suppose the pre-election polls show the following:

15  A B=C
25  A B C
10  B A C
10  B C A
25  C B A
15  C B=A

Here the polls show that B is the likely Condorcet winner, and that with
B out of the picture, A and C are equally likely to win.  For the 30
truncating voters, the expected utility of the outcome is zero.

If only 6 of the 15 A>B=C voters vote instead for A>C>B, and 6 of the
C>B=A voters vote instead for C>A>B, then B is defeated and the election
becomes a 50/50 lottery between C and A.  The expected utility of the
outcome for all of the A and C voters is now 0.5 (assuming 1.0 is the
utility of your favorite).

Note that either side can "cheat" and continue to truncate, but the cost
of being cheated is zero.  So as a sincere truncator you have nothing to
lose by engaging in the strategy, unless you think the other side WILL
engage in the strategy and you don't mind poisoning the well for future
elections in exchange for a one-time windfall.

Note also that this doesn't need to be a 50:50 lottery, so long as there
is reasonable uncertainty as to the outcome of the A vs. C race.


> > To expand this a bit, I can imagine a voter presented with a long list
> > of candidates who ranks the top few sincerely, and then decides he
> > doesn't care about the rest.  But instead of truncating, the voter
> > should probably rank these candidate in inverse order of their threat
> > potential, with any likely Condorcet winners ranked last.
> 
> As I thought I said above, your actual ranking placed every listed
> candidate above this "rest".  Listing one of these cannot help them
> against those you have already listed as better - only as preferred over
> those not listed before them.

Yes, but that last clause was the point of the above example.


> Not clear to me how "equal in the polls" matters, even if you believe the
> polls.  If they are equal than you could affect the result (but have said
> you do not care).  If not equal then it does not matter how you vote.

"Equal in the polls" matters in that it implies uncertainty about the
A:C outcome, which makes the above strategy possible.  Actually the
uncertainty is the important part; they don't necessarily have to be
equal, just that either side has a reasonable chance of winning the A:C
matchup.