Eric Gorr wrote:
At 6:04 PM +0000 11/11/04, Paul Crowley wrote:
On Thu, 11 Nov 2004 12:08:31 -0500, Eric Gorr <[EMAIL PROTECTED]> wrote:
hummm....there appears to be two opposing points of view here.
Chris B. claims that IIA satisfaction does imply ICC satisfaction. Markus S. claims that it does not.
I'm responsible for the edits to that page that make that claim, but if it's wrong please do fix it. Markus S - I'm very surprised that IIA does not imply ICC, could you give an example? I mean the strong version of IIA, the one that no reasonable system satisfies.
I think you mean the strong version of IIA which no ranked ballot method can satisfy.
Unless I am mistaken, Approval Voting does satisfy IIA
It only meets IIA under the assumption that adding or removing a candidate does not affect people's votes on the other candidates. This is an unrealistic assumption.
For example, suppose that the votes are:
5: A 4: AB 3: B 1: BC 9: C
Then A has 9 votes, B has 8 votes, and C has 10 votes, so C wins. But suppose that A withdraws from the election, and so the votes become
5: (spoiled ballots) 7: B 1: BC (spoiled ballot) 9: C
But I think it's more realistic to expect that the 6 "spoiled ballot" voters would instead vote for their choice between B and C, which would make the outcome
12: B (the former A, AB, and B voters) 10: C (the former BC and C voters)
A's withdrawal from the election changes the winner from C to B, and thus Approval voting fails IIA.
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