[EM] SCRRIRVE; my folly

Kevin Venzke stepjak at yahoo.fr
Tue Jan 20 20:18:02 PST 2004


 --- James Green-Armytage <jarmyta at antioch-college.edu> a écrit : 
> 	Here's why I think it's probably Condorcet efficient: Just as an IRV
> winner must have a pairwise beat over at least one other candidate, I
> think that a reverse IRV winner (an IRV winner with reverse rankings)
> might have to have at least one pairwise loss against another candidate.
> Thus SCRRIRVE can't eliminate a Condorcet winner. Anyway, if it's not
> Condorcet efficient, then it's dern close. 

That is very interesting reasoning.  I can't think if there's a flaw in it.

> I don't know what the effect of
> the symmetrically created ballots are as far as Condorcet efficiency.
> Also, I don't know whether it's efficient with respect to Schwartz, Smith,
> or Condorcet loser.

I can't tell if you're aware of this, but symmetrically completing ballots
can't create or delete pairwise victories.  In other words "Schwartz" (as
a method) meets SC (the criterion).  Also, the method could be called
SCCCRRIRVE; you could complete the ballots before taking the Schwartz set.

> 	Anyway, if SCRRIRVE is Condorcet efficient, then there is no need to call

Well...  That's only true if SCRRIRVE is also "Schwartz efficient."  Maybe
it's not.

> Perhaps someone else (Markus?) can tell us why Raynaud
> isn't discussed more often. I imagine that there is a good reason for it,
> since Raynaud is just about as obvious as WV minimax / sequential
> dropping, and thus must have been discussed at some point.

Raynaud can give weird results:

11 C>A
7 A
9 B
10 D>B

B>C 19 (margin 8), B>A 19 (margin 1), A>D 18, C>A 11 (m 4), C>D 11 (m 1), 
D>B 10.

Eliminate C and then A.  D beats B and wins.

Kevin Venzke
stepjak at yahoo.fr

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