[EM] are ranked pairs and river Schwartz-consistent?
Steve Eppley
seppley at alumni.caltech.edu
Wed Sep 15 21:40:37 PDT 2004
Hi,
James G-A wrote:
> I've often heard that ranked pairs is Schwartz consistent,
-snip-
No, but it elects within the top cycle, which is nearly
the same.
> As far as I can tell, the GOCHA set in this example is
> only {A}. A is surely undominated, and I cannot find any
> other sets of candidates other than {A B C D} which are
> also undominated. So, a Schwartz-efficient method should
> choose A with certainty.
> However, using ranked pairs, there is a tie between
> A and R, and if you use a basic tie-breaking ranking
> of the options method, there is a 50% chance that
> R will be elected.
-snip-
R tied A pairwise, which is fairly direct evidence that
society is split between R and A. The majority that
ranked another candidate over R is outweighed by the
larger majorities in that cycle. There's no majority
that would complain A should have been elected when
R is elected. So why worry?
I don't recall seeing any papers by Schwartz in which
he argued for Schwartz consistency over top cycle
consistency. Is there one? If so, what was his
justification?
--Steve
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