[EM] Condorcet Flavored PR Methods

[matt at tidalwave.net]

On 28 Sep 2002 at 16:17, Markus Schulze wrote:

> Dear Forest,
> 
> you wrote (27 Sep 2002):
> > A "Condorcet Flavored PR Method" is an M-winner election method that
> > (1) compares candidate subsets of cardinality M head-to-head, and
> > (2) does the comparison in such a way that the winning combination
> > of any head-to-head comparison provides better PR representation
> > than the loser subset, and
> > (3) gives the win to the "beats-all" combination if there is such
> > a subset.
> 
> Tideman has proposed such an election method:
> 
>     T. Nicolaus Tideman, Daniel Richardson,
>     "Better Voting Methods Through Technology: The
>     Refinement-Manageability Trade-Off in the Single
>     Transferable Vote," PUBLIC CHOICE, vol. 103,
>     p. 13-34, 2000 (http://www.econ.vt.edu/tideman/rmt.pdf)
> 
I doubt that CPO-STV consistently gives the winning outcome "better PR 
representation" than the losing outcomes.  It only transfers votes when at least one 
candidate is common to both outcomes.  Since it is the transfer that makes it PR 
and since the proportion of outcome pairs that have common candidates decreases 
as the number of candidates increases relative to the number of winners, it seems 
to me that CPO=STV is semi- or quasi-PR.

Another way to compare outcomes is to count all pairwise candidate winning votes 
between the two outcomes, substituting approval count for winning votes when the 
two candidates being compared are the same candidate thus favoring those 
outcomes with candidates that have high approval counts.

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