[EM] "good method" ?

[Chris Benham]

Rob LeGrand wrote (13 Feb 2010):

<snip>
"My only point is that the
Condorcet criterion should perhaps require majorities if we are to insist
upon it.  Here is a better example of my point:

41:A>B=C>D
29:B>D>C>A
30:C>B>A>D

C is the Condorcet winner even without a true majority over B.  I don't
see that it would embarrass a method to choose B as the winner of this
election.  Do you?"
--


Rob,

Yes, taking this as pure rankings information. I would hope and expect
that the method's result would be unaffected by the presence of the 
Pareto-dominated Majority Loser candidate D.

So tidying up by dropping D from the ballots we get

41: A
29: B>C
30: C>B

C is plainly stronger than B.

I don't see any good philosophical reason why we would want to isisist on
compliance with Condorcet(Gross) but not Condorcet(Net). 

The concept of doing so tends to be vulnerable to Irrelevant Ballots.
X may be the Condorcet (Gross) winner (and so must win) and then we can
add a few bullet-votes for a very weak candidate that all the other ballots ignore,
raising the the majority threshold so now X is only the Condorcet(Net) winner and
allowed to lose.

If there is some desirable criterion compliance that is compatible with Condorcet
(Gross) but not the stronger Condorcet(Net), then that could be a theoretical reason
for (as you suggest)  insisting  on compliance with Condorcet(Gross) but not Condorcet
(Net).


Chris Benham


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