[EM] unintended changes in pairwise preferences

[Kevin Venzke]

Hello,

--- Stephen Turner <smturner0 at yahoo.es> a écrit :
> This has raised two questions for me.
> (1) Is it known whether there can exist a procedure in
> which a pair (P1,P2) can never be reversed in the
> social ordering by changing only the unrelated (P3,P4)
> pairwise preferences in one or more ballots?  
> Dictatorship and anti-dictatorship obviously satisfy
> this, but what about anything else?

This is ruled out by IIA, isn't it?

> (2) Among the criteria we usually discuss on this
> list, we do not have one on "stability", which should
> mean something like: "a small change in the ballots
> should change the outcome as rarely as possible". 
> This seems desirable.  Has it already been discussed
> somewhere?

I think, if such a criterion came to be valued, it would result in
a lot of insensitive methods that behave more like Approval than any
ranked method.

I'm lately interested in ranked methods with a strong approval 
component, but I consider the insensitivity to be an annoyance
rather than a virtue: Why use a ranked ballot at all if additional 
voters rarely make a splash?

Kevin Venzke



	

	
		
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