[EM] Methods, and the criteria they satisfy

Stephane Rouillon stephane.rouillon at sympatico.ca
Fri Sep 19 07:27:01 PDT 2003


Ms. Galletly,

I find all of thiose criteria a bit extreme but I understand a rigorous
classification is needed. However I can tell you about the method I
prefer:
Tideman's Ranked Pairs.

> 5). ...  I've read that Tideman's Ranked Pairs fails SDSC and
> WDSC, but the other two completion methods meet them.
>
>From what I had understood, it depends on the criteria you use. Ranked
Pair
exist in several forms: margin -RP(m), relative margin -RP(rm)- and
winning votes-RP(wv). RP(m) is the simplest, RP(rm) is the most
representatives for sincere ballots (In My Humble Opinion) and RP(wv) is
the most resisitant to unsincere truncation strategies. So the above
comment maybe true only for RP(m).
Still, I know that RP(wv) garantees to protect a strong Condorcet winner
(with a majority against every other candidate). RP(m) and RP(rm) only
protect a stronger Condorcet winner (with 66% support against every
other candidate). Neither can protect
a weak Condorcet winner.

However, I have designed a RP(winning votes) method on an extended graph
that I think can protect even a weak Condorcet Winner. This method like
any Condorcet Ranking
can be generalized to produce weights as an output so to be used in a PR
multiple-winners method.

I hope it helps,
S. Rouillon
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