Jan, IRV elects C like all of the other methods if the B faction doesn't truncate. But IRV elects A when the B faction truncates. Of course, with this knowledge, the B faction isn't likely to truncate, and as you say C will be elected.
The trouble with IRV is that in the other scenario when the B faction truncates sincerely because of detesting both A and C, IRV still elects A instead of B. > Date: Sat, 6 Aug 2011 11:46:12 -0600 > From: Jan Kok > To: Jameson Quinn , Election Methods Mailing > List > Subject: Re: [EM] Chicken problem (was: SODA and the Condorcet > criterion) > >>> 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. > > > ------------------------------ > > _______________________________________________ > Election-Methods mailing list > [email protected] > http://lists.electorama.com/listinfo.cgi/election-methods- > electorama.com > > End of Election-Methods Digest, Vol 86, Issue 18 > ************************************************ > ---- Election-Methods mailing list - see http://electorama.com/em for list info
