[EM] STAR cloneproof variant based on Score Chain Climbing

[Kevin Venzke]

Hi Ted,

Ted Stern wrote:
> Here's a proposal for a STAR variant that handles clones:
> 
> Top two score winners (A and B), plus the score winner when you exclude the
> top score winner ballots (by score weight), that's the clone-proof part. Call
> that the exclusive winner, X. In other words, if a ballot gives a score of 5
> out of 10 to the top score winner, remove half that ballot's weight.

Is it allowed for B and X to be the same candidate? (I'm not sure it's totally
ruled out that even A and X could be the same.)

If a ballot gave A a 10/10, I assume all weight is removed when determining X.
 
> Eliminate any candidates defeated by X.  If more than one remains, the winner
> is the one who defeats the other.

When you say "if more than one remains" I assume you mean "of A and B." Or
possibly "of A, B, and X."

When you say "the winner is the one who defeats the other," this is a second
round of voting, correct? So in all cases of this second round it will be
between two of {X,A,B}?

> This follows the logic of Forest Simmons' Score Chain Climbing to resolve
> cycles.
> 
> The clone problem is that A and B could be clones. Removing A's ballot
> contributors finds the non-clone while avoiding pushover incentive. If X
> defeats both A and B, it's likely the CW. Otherwise, whichever of A or B is
> defeated by X is "weaker" (low probability, but possible in cycles). 
> Using a lower-scoring candidate as an eliminator reduces burial incentive.

Not sure I follow. The claim is counter-intuitive because usually a candidate to
be given artificial preferences is a weaker one (lower-scoring) because the
insincere voters believe this candidate can't win, and don't wish for him to win.

For example in your case if either A or B (doesn't matter) believes they will
beat X pairwise then they are able to try to use X to knock the other of A/B
out. Just rate X a 1/10, and the other 0/10. No?

As I say, I think it's not chain climbing generally, but TACC(implicit)
specifically, that has anti-burial value.
 
> Why do I propose finding X that way instead of by a Hare or Droop quota?
> Well, for one thing, it's a summable process. Next, if A has >50% approval,
> A and B are probably the two candidates to choose from anyway. If A has
> <50% approval, X is being found with something like a Hare quota, moving
> more toward Droop as A's approval decreases.
> 
> Your thoughts?

I think the goal of decloning the election is a bit different from the goal of
selecting the "best" two finalists for a runoff (if this method actually has a
runoff, wasn't sure there). So I'm not so worried if you don't use some more
"proper" decloning method like a quota.

Kevin