[EM] SSD, RP wrap-up

Markus Schulze schulze at sol.physik.tu-berlin.de
Sat Apr 21 03:48:45 PDT 2001

Dear Mike,

you wrote (19 Apr 2001):
> What are RP's advantages? It meets Steve's output ranking
> consistency criteria. If that's the most important thing to
> someone then they'd prefer RP to SSD or Cloneproof SSD.

Not all of Steve Eppley's criteria are "output ranking
consistency criteria." Some of them also refer to the winner.
For example, his "Immunity from Squawking Criterion" says:

   Suppose that candidate A would be elected, if candidate
   B didn't run. Suppose that candidate A pairwise beats
   candidate B. Then -when candidate B does run- candidate B
   must not become the new winner.

Steve Eppley mentioned that only Ranked Pairs meets this


You wrote (19 Apr 2001):
> RP can choose outside the initial Schwartz set. SSD & Cloneproof SSD
> will never do that. Choosing outside the initial Schwartz set isn't
> serious. I'm not aware of it causing a strategy problem, but that
> doesn't mean I'm saying it doesn't. But it's an embarrassment, and,
> as I said before, an aesthetic gaffe. And an avoidable one, since
> we've got excellent methods that don't have that failing.

In so far as your claim that Ranked Pairs could choose outside the
Schwartz set seems to be your main argument against Ranked Pairs,
it would be very helpful if you could post an explicit example where
Ranked Pairs actually chooses a candidate outside the Schwartz set.
Otherwise your claim that Ranked Pairs could choose outside the
Schwartz set seems to be not justifiable.

Markus Schulze

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