[EM] IRV in San Francisco

[Eric Gorr]

At 1:47 PM -0500 11/12/04, Dave Ketchum wrote:
>On Fri, 12 Nov 2004 13:06:23 -0500 Eric Gorr wrote:
>
>>At 7:44 AM -0800 11/12/04, Justin Sampson wrote:
>>
>>>On Fri, 12 Nov 2004, Eric Gorr wrote:
>>>
>>>  > Well, it will cause IRV to fail the Independence of Clones Criterion and
>>>
>>>>  thereby be subject to a spoiler effect again.
>>>
>>>
>>>Doesn't IRV suffer from spoiler effects anyway?
>>
>>
>>Depends.
>>
>>The method itself passes the ICC, so spoilers cannot come from there.
>>
>>It, of course, fails IIA (as all ranked ballot methods do), so 
>>spoilers in this context still exist. Of course, since no ranked 
>>ballot methods pass IIA, talking about spoilers in this context is 
>>not very interesting.
>>
>>Are there more directions from which spoilers can appear?
>>I am currently not aware of any.
>>
>I do not keep up with the alphabet soup, but IRV and Condorcet disagree as
>to winner in the following, and I see Nader as a spoiler for IRV:
>
>
>40 Bush
>35 Nader, Kerry
>25 Kerry
>
>Condorcet sees 35 Nader as ignorable and then 60 Kerry vs 40 Bush
>
>IRV discards 25 Kerry; then sees 40 Bush vs 35 Nader.

Unless I am mistaken, this would show a failure of Independence of 
Irrelevant Alternatives (IIA).