[EM] A few methods that pass, and a few methods that fail CD

[Kristofer Munsterhjelm]

On 10/19/2012 04:35 AM, Michael Ossipoff wrote:
> A few methods that pass CD:
>
> ICT
> Symmetrical ICT
> MMPO
> MDDTR
>
> A few methods that fail CD:
>
> Beatpath, RP, Kemeny, VoteFair, MinMax(wv) and apparently all
> traditional unimproved Condorcet versions.
>
> Approval and Score don't pass CD either. But, as I said before, it's
> so easy to automatically avoid the chicken dilemma nuisance with a
> rank method that there's no excuse for a rank method to fail CD, and
> so no rank method that fails CD should be considered.

All of the methods above fail independence of clones. Therefore, I 
disagree that "there is no excuse for a method to fail CD", unless you 
can show that it's possible to construct a method that passes both clone 
independence and CD. As it stands, the CD methods and the wv/margins 
methods are mutually Pareto-nondominated with respect to each other*.

(That is, assuming that ICT reduces to Condorcet//FPP if there are no 
truncated votes nor equal-rank ones. If that is wrong, please tell me 
what method ICT reduces to when all voters rank every candidate, ranking 
nobody equal.)

* Perhaps some of the CD methods dominate other CD methods, and perhaps 
some of the non-CD methods dominate other non-CD methods, but that's 
besides the point here.