[EM] Chicken problem (was: SODA and the Condorcet criterion)

[Jan Kok]

>>> To review for other readers, we're talking about the scenario
>>>
>>> 48 A
>>> 27 C>B
>>> 25 B>C
>>>
>>> Candidates B and C form a clone set that pairwise beats A, and in fact C
>>> is the Condorcet Winner, but
>>> under many Condorcet methods, as well as for Range and Approval, there is
>>> a large temptation for the
>>> 25 B faction to threaten to truncate C, and thereby steal the election
>>> from C.  Of course C can counter
>>> the threat to truncate B, but then A wins.  So it is a classical game of
>>> "chicken."
>>>
>>> Some methods like IRV cop out by giving the win to A right off the bat,
>>> so there is no game of chicken.

Wait a minute! IRV elects C in this scenario, if that is how the
voters actually vote, and those are the sincere preferences (A voters
have no preference between B and C).

Much as I hate to say it, IRV works OK in that scenario. On the other
hand, if the A voters prefer B over C, (as in the 2009 Burlington, VT
mayoral election, http://scorevoting.net/Burlington.html) IRV ignores
the preference and still elects C, which seems to be the wrong choice.