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 weakerbecause nothing >can pass IIA and meet three other desirable criteria.
> What ICC and IIA are you using?
Whichever ones you are.
Not necessarily.
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 proof.
Since we do not know if the resolute versions of ICC and IIA are directly related to one another, this statement is currently meaningless.
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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