[EM] Simple monotonicity question

[Kathy Dopp]

Kristofer,

In answer to your question below.

I could be wrong because I am not sure of the total number of
candidates in the contest, but I believe that the answer is "No,
nonmonotonicity can occur even when the Condorcet candidate wins."
This happened in the recent Aspen, CO city council election where if
75 fewer persons had voted for one of the candidates, he would have
won, but I believe that the actual winner was the Condorcet winner,
unless I'm mistaken.

Perhaps you can look into it by contacting Aspen. I believe that the
list of all voters' votes is available, but not the images of the
original ballots to check the accuracy of that list.

Kathy

Message: 4
Date: Sat, 20 Feb 2010 10:56:09 +0100
From: Kristofer Munsterhjelm <km-elmet at broadpark.no>
To: EM <election-methods at lists.electorama.com>
Subject: [EM] Simple monotonicity question
Message-ID: <4B7FB1B9.3080604 at broadpark.no>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Does nonmonotonicity in three-candidate IRV only happen when the
Condorcet winner is eliminated?

More generally, does a candidate-elimination method have to be able to
eliminate the Condorcet winner in a three-candidate scenario in order to
be nonmonotonic with only three candidates?