[EM] STAR

[Forest Simmons]

On Mon, Aug 21, 2023, 5:38 AM C.Benham <cbenham at adam.com.au> wrote:

> Toby,
>
> Also a run-off between the most two approved candidates still has STAR's
> clone problem.
>
>
> Some years ago I suggested that 2-round Top-Two Runoff  could be improved
> by using approval ballots in the first round
> and then having a runoff between the most approved candidate (the AW) and
> the candidate with the most approval opposition
> to the AW (i.e. is most approved on ballots that don't approve the AW).
>

This is a simpler way of specifying the candidate with the second greatest
Transferred Vote Count in Martin Harper's approval vote transfer scheme ...
which he invented as a tongue in cheek response to IRV voters' claims that
Approval failed "one person, one vote."

Here's my generalization of Martin Harper's idea to Score Voting:

Suppose that for each candidate X, TS(X) is X's Total Score... the sum over
all score ballots B, of B(X), the score assigned to X by B.

Then ballot B's (one and only) "transferred vote" should go to the
candidate X with the largest product
X*B(X).

So the analogous score runoff would be between the two candidates with the
most transferred votes as determined by this score vote transfer scheme.

>
> If the most approved candidate is cloned, the run-off becomes irrelevant.
>
> Spoken like someone who lives in parliamentist country. "Clones" aren't
> necessarily identical.  There could be slight political differences
> or one may be less corrupt, or one could just have a much better haircut.
>
> Parties being having incentive to each field two candidates (even if they
> are "clones") is maybe not too bad.  But STAR uses score ballots
> so there is a danger that there being two candidates from the same party
> might cause voters to not give both of them max score enough
> to stop both of them from making the final.
>
> However, I just don't think that STAR's failure here can reasonably be
> called a monotonicity failure.
>
> I think it is very much like one and it's claiming of bragging rights on
> that point over IRV is unfair and misleading.
>
> Chris
>
>
>
>
> On 20/08/2023 5:55 am, Toby Pereira wrote:
>
> Also a run-off between the most two approved candidates still has STAR's
> clone problem. If the most approved candidate is cloned, the run-off
> becomes irrelevant.
>
> Toby
>
> On Saturday, 19 August 2023 at 17:43:12 BST, Toby Pereira
> <tdp201b at yahoo.co.uk> <tdp201b at yahoo.co.uk> wrote:
>
>
> Chris
>
> It's not that I disagree with your views of STAR's behaviour as a method.
> And there are changes that could be made that would improve STAR, as you
> say. However, I just don't think that STAR's failure here can reasonably be
> called a monotonicity failure.
>
> Toby
>
> On Saturday, 19 August 2023 at 04:10:32 BST, C.Benham
> <cbenham at adam.com.au> <cbenham at adam.com.au> wrote:
>
>
> Toby,
>
> I wouldn't count this as a monotonicity failure because it involves
> decreasing Y's score as well as increasing X's.
>
>
>
> This is like a sophist's technical loophole.  Why do we particularly care
> about "monotonicity failure"? To avoid some hypothetical mild
> embarrassment?
> For the sake of marketing bragging rights?
>
> Or because it is related to Push-over strategy incentive/vulnerability?
> STAR is  much worse in that respect than IRV because there the strategists
> are entirely
> relying on other voters to both get their favourite into the final two and
> to there win the pairwise contest, so if too many of X's supporters try the
> strategy it
> could backfire.
>
> Whereas with STAR the strategists could be a bit cautious and give the
> weak candidate they are trying to promote into the final a score of max.
> minus one
> while also giving their favourite X max. points.
>
> That way all of X's supporters could use the strategy and it could still
> succeed.
>
> The 0-5 score ballot is too restrictive (certainly for STAR)  Say, as I
> earlier advocated, the voters rank however many candidates they want to and
> give an approval cutoff wherever
> they want, and we elect the pairwise winner between the two most approved
> candidates.
>
> That would be very similar to STAR (0-5 score ballots) but wouldn't it be
> better?  And also a method that fails mono-raise and Condorcet and many
> other criteria
> and is obviously terrible?
>
> Chris
> On 17/08/2023 9:47 pm, Toby Pereira wrote:
>
> I wouldn't count this as a monotonicity failure because it involves
> decreasing Y's score as well as increasing X's. Mono-raise may have been
> defined specifically for ordinal ballots where raising a candidate
> inevitably pushes others down. Whereas with a rated ballot, I think one
> would be more likely to define monotonicity criteria in terms of increasing
> a candidate's score while leaving all others the same.
>
> Toby
>
>
> On Thursday, 17 August 2023 at 05:43:00 BST, C.Benham
> <cbenham at adam.com.au> <cbenham at adam.com.au> wrote:
>
>
> Toby Pereira wrote:
>
> I'm not a fan of STAR, but I am still interested in seeing how it stands
> up to scrutiny given that it has a following. (Actually I'm not aware of
> how STAR fails monotonicity. I was under the impression that it passed.)
>
> Toby,
>
> To give you a bit of a preview before I get around to cooking up all the
> examples, nothing with such obvious Push-over incentive can meet mono-raise
> (aka "monotonicty")
>
> Suppose  X beats Y in the final.   Now suppose on some ballots with Y
> above X, we raise X so it is now above Y.  That could reduce Y's score
> enough for it to be replaced in the final
> by Z, a candidate that pairwise beats X.
>
> Voters who are mainly concerned to have their favourite X win and are
> fairly certain that X will reach the final will have a strong incentive to
> give X max points (5) and then also
> give a 4 (or even a 5) to all those candidates that they think X can beat
> pairwise.
>
> If enough voters use that strategy and it fails, both the finalists could
> be candidates with little sincere support.
>
> Chris Benham
>
> O
>
>
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