The Condorcet-Kemeny method does allow candidates to be ranked at the
same preference level, and no special calculations are needed to handle
these ballots. Such "ties" can occur at any combination of preference
levels. The interactive ballots at VoteFair.org allow such "ties" and,
more broadly, allow any one oval to be marked for each choice. (On a
paper-based version, if a voter marks more than one oval, only the
left-most marked oval is used.)
I've addressed the "clone dependence" issue previously, yet I'll repeat
the important points: Exact clones (which is what clone dependence
assumes) are very rare in real elections, and circular ambiguity (that
includes the winner) is not common (because Condorcet winners are more
common), so the combination of these two events -- which is what must
occur in order to fail the clone independence criteria -- is extremely rare.
When I get time to reply to Warren's other message I'll address the
"computational intractability" misconception.
Richard Fobes
On 9/13/2011 2:39 PM, [email protected] wrote:
The problems with Kemeny are the same as the problems with Dodgson:
(1) computational intractability
(2) clone dependence
(3) they require completely ordered ballots (no truncations or equal
ranking), so they do not readily adapt to Approval ballots, for example.
In my posting several weeks ago under the title "Dodgson done right" I
showed how to overcome these three problems. (The same modifications do
the trick for both methods.) However, much of the simplicity of the
statements of these two methods (Dodgson and Kemeny) gets lost in the
translation.
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