[EM] STAR challenge
Forest Simmons
forest.simmons21 at gmail.com
Tue Jun 7 19:06:45 PDT 2022
Actually, you have just described the winner of Benham,Score, which
successively eliminates the lowest score candidates until there remains one
candidate that defeats all of the other remaining candidates.
RSTAR also starts at the bottom, but eliminates losers of bottom score
pairwise contests until there remains a candidate that defeats all of the
other remaining candidates.
It is easy to check that in the case of three Smith members, (1) Score
Chain Climbing, elects the highest score Smith member that defeats the
lowest score Smith member ... (2) Benham-Score elects the lowest score
Smith member that defeats every higher score member, and (3) RSTAR elects
the highest score Smith member.
Since public elections rarely have more than three Smith members, that
summary pretty much tells us what to expect from these three methods.
The best one to propose/adopt depends on simulation results and which
method has the simplest, most appealing counting procedure(s), since each
of them can be tallied by several different procedures to check the result
of the 'official' procedure.
If burial is a perceived threat, I would recommend Chain Climbing.
Otherwise, I would recommend the Single Pairwise Elimination description of
RSTAR ... unless it turns out that some description of Benham,Score turns
out to be more appealing to the lay voter.
I am assuming that all three of these will have roughly the same VSE, which
we already know to be better than plain Score from published simulations in
the case of Smith,Score and plain STAR. If one does stand out, we should
see if the voters care about the difference.
The beauty of the above three methods is that they give us Independence
from Smith Dominated Alternatives (ISDA) without having to construct the
Smith set, or even mention it. In fact the simplest procedures have no need
to even mention the word Condorcet, which some people have been sternly
warned against ... like countries with state religions warning their
citizens against reading any literature from non-state religions, or
Christian priests prohibiting Bible reading by their parishioners. [In
sixteenth century England, William Tyndale was burned at the stake for
making an English translation of the Bible so that common English speakers
could read it for themselves.]
-Forest
El mar., 7 de jun. de 2022 4:29 p. m., Andy Dienes <andydienes at gmail.com>
escribió:
> Hi Forest,
>
> If I am understanding RSTAR correctly, it should be the same as electing
> "the lowest score candidate that defeats all of the higher score
> candidates," right?
>
> It certainly sounds intuitive. How would it compare to, e.g. Score Chain
> Climbing?
>
> -Andy
>
> On Tue, Jun 7, 2022 at 6:36 PM Forest Simmons <forest.simmons21 at gmail.com>
> wrote:
>
>> Benham-Range is ISDA (department of agriculture?). In fact, it elects the
>> lowest score candidate that defeats all of the higher score candidates.
>>
>> So it is a simple proposal with lots of heuristic rationales and criteria
>> compliances going for it.
>>
>> Another similar ISDA proposal that I call RSTAR for reasons soon
>> apparent, always elects the highest score Smith candidate in the three
>> candidate case:
>>
>> RSTAR like STAR can be formulated as a procedure that takes a set of
>> score ballots as input, and selects as output a winner from among the
>> scored candidates on the input ballots.
>>
>> For comparison, here's a formulation of STAR in that format:
>>
>> Let beta be a set of Score ballots.
>>
>> Then the STAR output STAR(beta) is the winner of the two candidate runoff
>> between X=Score(beta) and Y=Score(beta'), where beta' is the set of ballots
>> with candidate X temporarily removed.
>>
>> The RSTAR output RSTAR(beta) is the winner of the two candidate runoff
>> between X=Score(beta) and Y=RSTAR(beta'), where beta' is the set of ballots
>> with candidate X temporarily removed.
>>
>> See the comparison (and tiny contrast)? If you see it and understand it,
>> then you know that RSTAR must stand for Recursive STAR.
>>
>> This is the most succinct formulation of SPE(Score), Sequential Pairwise
>> Elimination with a Score based agenda.
>>
>> Since SPE is a respectable, classical method with a hoary history of use
>> in deliberative assemblies, as prescribed by Robert's Rules of Order, this
>> would be an impeccable public proposal.
>>
>> The Recursive formulation should serve only as a bridge between STAR and
>> the less exotic SPE formulation; we don't want any heads to explode!
>>
>> What say ye?
>>
>> -Forest
>>
>> ["Ye" is an archaic form of "ya'll" or "youse guys" ;>)]
>>
>> El mar., 7 de jun. de 2022 10:51 a. m., Forest Simmons <
>> forest.simmons21 at gmail.com> escribió:
>>
>>> Very good observations ...and I like your method suggestions.
>>> Benham-Range (without the renormaliization),unlike ordinal Benham, should
>>> also be monotone and precinct summable if I understand it correctly.
>>>
>>> El mar., 7 de jun. de 2022 5:12 a. m., Kristofer Munsterhjelm <
>>> km_elmet at t-online.de> escribió:
>>>
>>>> On 07.06.2022 05:49, Forest Simmons wrote:
>>>> > VSE (voter satisfaction efficiency) simulations seem to bear out that
>>>> > STAR is a significant improvement over plain old Score voting, but not
>>>> > quite as good as Score restricted to the Smith Set.
>>>> >
>>>> > So it appears that simple STAR is the low hanging fruit worth some
>>>> trial
>>>> > and error tweaking experiments to convert it into the best public
>>>> proposal.
>>>>
>>>> I'd say there are two ideas of generalizing STAR, call them cardinal and
>>>> ordinal. The cardinal one should preserve the property that in an LCR
>>>> election where the centrist is highly rated, he wins, but where he's
>>>> ranked poorly, he loses. (Making this cloneproof without just degrading
>>>> to plain Range is hard!)
>>>>
>>>
>>> That's the idea of my suggestion ... pit the Martin Harper Lottery top
>>> probability candidate against the score winner ... or I could have
>>> suggested a runoff between the two top probability lottery candidates.
>>>
>>> Better yet ... do Sequential Pairwise Elimination on the support of the
>>> MH Lottery, where the agenda order is from least to greatest probability.
>>>
>>> The MH Lottery is based on an idea for
>>> Range-->Plurality DSV: given all of the Range ballots, how should you
>>> decide which candidate ballot B should support (from the superstitious
>>> one-person-one-vote point of view)?
>>>
>>> Answer: the candidate X should have a high score B(X) on ballot B, and
>>> should have high support from the other ballots as well. The support of X
>>> from the other candidates can be gauged by its total score S(X). So X
>>> should be the candidate that maximizes the product B(X)S(X).
>>>
>>> Which is why the Martin Harper Lottery probability for candidate X is
>>> the percentage of the ballots B for which X maximizes the product B(X)S(X).
>>>
>>> [In 2001 Martin Harper posted to the EM list a definitive explanation
>>> for diehard IRV supporters of how Approval utterly satisfies "one person
>>> one vote" by way of a memorable Maxwell's Demon vote shuttling mechanism.
>>> So it is only fitting that Harper get the credit for this lottery idea!]
>>>
>>>>
>>>> The ordinal one, on the other hand, should find the CW whenever he
>>>> exists, and probably also elect from some nice set (Smith, Landau or
>>>> Banks). STAR itself doesn't do this.
>>>>
>>>> > Some brainstorming is definitely in order. Ted Stern has been working
>>>> on
>>>> > this.
>>>> >
>>>> > Some possible directions:
>>>> >
>>>> > 1. Simplify the description of Score restricted to Smith to be on a
>>>> par
>>>> > with the simplest description of STAR
>>>> >
>>>> > 2. Find a better runoff opponent for the score winner.
>>>> >
>>>> > 3. Compare STAR with Score Sorted Margins and Sequential Pairwise
>>>> > Elimination based on a Score agenda.
>>>> >
>>>> > Here's one idea:
>>>> >
>>>> > For each ballot B, and each candidate X, let B(X) be ballot B's score
>>>> > for candidate X. Let S(X) be the sum over B of B(X). Then the score
>>>> > winner is the candidate X that maximizes S(X). Elect the winner of the
>>>> > runoff between the score winner and the candidate X that on the
>>>> greatest
>>>> > number of ballots B, maximizes the product B(X)S(X).
>>>>
>>>> I haven't thought about it in detail, but I think Range's de jure IIA
>>>> compliance implies that Benham-Range and BTR-Range are both Smith. They
>>>> might even be equivalent to Smith,Range. So if you want to look for a
>>>> simpler way of explaining Smith,Range, those may be it.
>>>>
>>>> My thinking is like this, for Benham-Range:
>>>>
>>>> Benham-Range eliminates the current Range loser until there's a CW.
>>>> Since Range passes IIA, eliminating without normalization doesn't change
>>>> the order of the other candidates. Hence all but one Smith set member
>>>> will be eliminated, after which the highest scoring Smith set member
>>>> becomes the CW and wins. So Benham-Range is just Smith,Range and may be
>>>> easier to explain.
>>>>
>>>> Benham-BTR I'm much less sure about because it protects the loser who
>>>> pairwise defeats the other. This is more like STAR. It might be that a
>>>> prospective loser is protected all the way up the Smith set, and then
>>>> beats the highest rated Smith set member pairwise -- unless such a
>>>> scenario is impossible.
>>>>
>>>> For runoffs, I think you could argue in two ways. Either the runoff is
>>>> about telling two quite good candidates apart, or it's about giving each
>>>> faction of the electorate "their" candidate to vote for. The former
>>>> suggests (if it's a manual runoff) just picking the two Smith set
>>>> members with the highest rating; the latter, something more like "the
>>>> candidate rated highest by voters who rated the first candidate low".
>>>>
>>>> If I had to choose, I'd probably go for the former, though it could
>>>> affect the turnout in the general: if both candidates are good, a lot of
>>>> voters may simply decide not to vote in the general.
>>>>
>>>> Automating the former, STAR would probably do a good job because it's
>>>> unusual for a candidate to be the CW yet not in the top two by highest
>>>> rating. At least it gets the bang for the buck award, even if it's not
>>>> perfect :-)
>>>>
>>>> -km
>>>>
>>> ----
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>
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