[Election-Methods] Clone related problems in Range/Approval Juho

[Kevin Venzke]

Hi,

--- Juho <juho4880 at yahoo.co.uk> a écrit :
> On Apr 17, 2008, at 16:39 , Kevin Venzke wrote:
> > Hi,
> >
> >>>> The claim that I don't recall having seen before is that in  
> >>>> Range and
> >>>> Approval it makes sense to the parties not to nominate multiple
> >>>> candidates.
> >
> > I've made this claim as well. When we're lucky enough to have three  
> > viable
> > candidates I tend to assume that either the center is running as an
> > independent, or one of the flank candidates is nominated by a (mostly
> > futile) third party.
> 
> Makes sense. I think it is a good approach to evaluate all the  
> plausible/probable basic scenarios. (Better than generic claims alone.)
> 
> > The harder claim is that this applies also to rank methods, though I'm
> > confident it does.
> >
> > My goals in designing a single-winner method would be to provide  
> > incentives
> > to voters and candidates that make it possible to have three viable
> > candidates, and elect the one (when he exists) which is the pick of  
> > the
> > "median voter."
> 
> I guess most single winner utility functions point approximately at  
> the "median voter" opinion, with the assumption of a linear order of  
> candidate opinions and voter preferences.

Yes, but there are many pitfalls involving incentives to truncate and
compromise. There won't be a perfect solution, but perhaps it will be
slightly easier to identify the possibilities if we stick to evaluating
scenarios that only have three viable candidates.

> > If the method fails (picks a bad winner) when the field
> > can't be narrowed to three viable candidates in time for the  
> > election, or
> > when the candidates can't be interpreted to fit on a 1D spectrum,  
> > I'd say
> > that's ok. The first problem is self-correcting, and the second one
> > shouldn't be all that common.
> 
> The next common candidate opinion space could be one with two  
> dimensions. One dimension may be enough to cover most basic cases but  
> there may be also other quite common patters that may resemble having  
> two dimensions, having two centrists with somewhat different profiles  
> etc.

However, it shouldn't matter too much even when there is more than one
dimension. With three candidates one can always draw a triangle at worst.
Hopefully the candidate opposite the longest edge can be identified as the
center candidate, with voter strategies responding to this perception
appropriately.

Kevin Venzke

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