[EM] Kemeny challenge

[Richard Fobes]

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, fsimmons at pcc.edu 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.