[EM] Endorsement for STAR voting

[Kristofer Munsterhjelm]

On 2024-03-19 02:05, Rob Lanphier wrote:
> Hi folks
> 
> I was asked to provide a quote supporting STAR voting by the Equal.Vote 
> Coalition (equal.vote <https://equal.vote>).

[snip]

> I think the Condorcet winner criterion (CWC) matters a lot more than
> "cardinal" advocates often suggest, but it's almost impossible for me
> to imagine a credible election scenario where the STAR winner and a
> strictly CWC-compliant method would differ.   More to the point, with that final
> pairwise comparison, STAR virtually guarantees that a majority of voters 
> prefer the winner to the runner up.  And it's 1000% better than RCV/IRV 
> as promoted by FairVote.

The obvious thing that comes to mind that could make STAR fail Condorcet 
is the clone problem. It doesn't even have to be a deliberate strategy: 
it could just emerge from the incentives. Suppose that there are three 
parties: Left, Center, and Right. Say that Left often is the Range 
winner, but the Left-first voters is a minority so Center comes in 
second and wins the runoff.

Then a second near-Left party has an incentive to grow, because if it 
can get strong enough, it knows that the left voters will also give it a 
high rating, so that the runoff now consists of two left-wing 
candidates, and thus one of them will win. If the rules permit a party 
to field multiple candidates, then it's even easier: the existing Left 
party can just field two.

Over time, this incentive to entry could reduce STAR to Range.

I agree that if we are to take strength of preference seriously (in the 
vNM sense, as I described in my other post), then it should, as you put 
it, take nuance into account, but not too much of it. I have some 
thoughts about how that could be done (I've written posts about it), but 
the methods would be considerably more complex.

Or if you're on the ordinal side of the divide, 
Smith//Range(renormalized) would fix the clone problem for rated clones. 
But it wouldn't be monotone.

The clone problem and entry incentive could be detected by simulation by 
replicating James Green-Armytage's work in the paper where he showed 
that IRV has an exit incentive. To my knowledge, nobody has done so yet, 
which would explain why you haven't seen any simulations of that form.

-km