[EM] IRV in San Francisco
eric at ericgorr.net
Tue Nov 16 14:24:36 PST 2004
At 4:03 PM -0600 11/16/04, Paul Kislanko wrote:
>Eric Gorr replied to my questions:
>> At 3:14 PM -0600 11/16/04, Paul Kislanko wrote:
>> >No one can be added or removed
>> >from a ballot after the votes have been counted,
>> Sure one can...just do it and recalculate.
>> >so by this distinction
>> >there is no such thing as an IIA spoiler.
>> I believe there is.
>> Compute the winner.
>> Start removing candidates and see if you can get the winner to change.
> > If the winner changes, you have a spoiler via IIA.
>That's what I said below - this is an analytical tool to determine how a
>method works logically.
So, you now believe there is such a thing as an IIA spoiler?
> > >ICC is just a weaker version of IIA, and has to be weaker
>> because nothing
>> >can pass IIA and meet three other desirable criteria.
> > What ICC and IIA are you using?
>Whichever ones you are.
There are multiple _VERSION_ of the criteria, which is why I asked.
>It wasn't ME that claimed that the difference was in
>ICC the candidates were already on the ballot, but to be precise we note
>that in your reply you said that in IIA they were on the ballot and you just
>remove them and add them back in.
You misunderstand, the ICC spoiler comes from neither removing nor
adding candidates - they are simple there being a spoiler and one can
see them as a spoiler without taking any further action.
For example, if a set of clones can obtain > 50% of the first place
votes, but no candidate in the clone set wins, they are spoilers.
This, as near as I can determine, has nothing to do with IIA.
> > On what basis do you call the ICC a weaker version of IIA?
>> Does your statement imply that if a method passes Dr. Arrow's IIA, it
>> must pass Dr. Tidemans ICC?
>I make no such claim,
You clearly stated:
ICC is just a weaker version of IIA
So, one what basis do you make that claim?
The claim is false, if you are using the non-resolute versions of IIA
& ICC, as Markus previously showed.
>If ICC is related to IIA and a
>method can meet Arrow's other three and also meet ICC, then per force ICC
>must be a weaker criterion than IIA, else there would be a flaw in Arrow's
Since we do not know if the resolute versions of ICC and IIA are
directly related to one another, this statement is currently
However, a claim has been make that if a ranked ballot method passes
Dr Arrow's IIA it must pass Dr. Tideman's ICC which I believe would
mean there is a direct relationship between them and that ICC is a
weaker version of IIA since ranked ballot election methods can pass
ICC, but not IIA.
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