[EM] Condorcet methods - should the cycle order always determine the result order? (Toby Pereira)

Forest Simmons fsimmons at pcc.edu
Tue Nov 4 14:46:54 PST 2014


You mentioned Kemeny.  The very purpose of Kemeny is to determine a "social
order," namely the one that minimizes the average "distance" from that
order to the ballot orders..

The trouble with Kemeny is that the choice of metric for the "distance:" is
clone dependent: changing the size of a clone set changes the number of
transpositions of order to move a candidate past that set.

However, if cardinal ratings (e.g. score ballots) are used, then clone
independent metrics can be substituted for the Kemeny distance. I once
posted a message to this list describing a clone free technique for
converting a set of ordinal ballots into a set of ratings  Then based on
those ratings it was possible to define "Kemeny Done Right,"  Dodgson Done
Right," and "Borda Done Right."  Of these three "done right" methods, only
the latter fails the Condorcet Criterion.

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