[EM] Fixing IRV

Richard Moore rmoore4 at home.com
Tue Aug 7 19:10:30 PDT 2001

Roy One wrote:
> Much has been made of the flaws of IRV. Notably, that it fails to
> find
> the Condorcet winner when there is one, which casts serious doubt on
> its claim of supporting majority rule.
> I think we all know the source of the flaw: it doesn't use majority
> rule in elimination rounds.

Actually, IIRC, there is a proof somewhere in the literature
that elimination methods are not monotonic. So the initial 
flaw is that it uses elimination at all. True, there are 
better and worse ways of eliminating candidates, and IRV's 
antiplurality elimination is certainly one of the latter group.

I don't recall if I've heard Roy's proposal before. There 
have been a lot of proposals to address IRV's problems while 
still using an elimination method. This method sounds like a 
big improvement over IRV but if it isn't monotonic then it 
still has a major flaw.

Does anyone recall the theorem I mentioned above about 
elimination and monotonicity?


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