[EM] Re: CCSCRRIRVE (last 2 sentences corrected)

Chris Benham chrisbenham at bigpond.com
Sun Jan 18 05:00:01 PST 2004

In response to my posting:

I propose and reccomend this single-winner  Condorcet  compliant method:
Plain ranked-ballots, equal preferences and truncation ok.
1: Eliminate all candidates who are not members of the Schwartz set.
2: If  more than one candidate remains, then based on the symetrically 
completed (SC) and reversed rankings,
eliminate the candidate picked by the Alternative Vote (aka IRV).
Repeat steps 1 and 2 until only one candidate (the winner) remains.

Bart Ingles wrote (Sat.Jan.17,2004)

"I think that's equivalent to Coombs, which if anything is even more
vulnerable to burying than Borda.  You might as well use Borda as the
completion method, since the Borda score can be inferred from the
pairwise matrix."

It is not equivalent to Coombs. Here is an Adam Tarr example (with the 
candidates re-named)
Presumed sincere is:
49: R>C>L
12: C>R>L
12: C>L>R
27: L>C>R
100 ballots. C is the CW.
R voters truncate:
49: R
12: C>R>L
12: C>L>R
27: L>C>R
L>C>R.  L is eliminated and  C wins.
R voters bury:
49: R>L>C
12: C>R>L
12: C>L>R
27: L>C>R
R>L>C.   The Burying strategy backfires,  R is eliminated and  L wins.
If  this were Coombs, C (with the most last preferences) would be 
eliminated and  R would win.

Chris Benham

More information about the Election-Methods mailing list