[EM] Cloneproof STAR [Was "Re: STAR cloneproof variant based on Score Chain Climbing"]

[Ted Stern]

Read the page again.

https://electowiki.org/wiki/Definite_Majority_Choice

On Wed, Jul 27, 2022, 14:40 Forest Simmons <forest.simmons21 at gmail.com>
wrote:

>
>
> El mié., 27 de jul. de 2022 1:52 p. m., Ted Stern <dodecatheon at gmail.com>
> escribió:
>
>> Hi Forest,
>>
>> We discussed your proposed method back in 2004. It's basically the same
>> as Definitive Majority Choice, using score instead of Approval.
>>
>
> Actually, DMC sorts from the favorable to the unfavorable, whereas SPE
> sorts from the unfavorable to the favorable, like your top three proposal,
> only SPE starts from the very bottom of the score list instead of from the
> third one down.
>
>>
>> DMC(score) has a simple basic procedure, as you note, which is identical
>> to Smith//Score in the 3 candidate case, but is less satisfying for larger
>> cycles. Which is why I prefer Score Sorted Margins in general.
>>
>> Back at the start of the thread, I mentioned that I like STAR except for
>> the clone problem. The basic idea is that the score winner is good in
>> general, but a coarse discrete scale lacks resolution, so the runoff
>> increases satisfaction.
>>
>> STAR3 is a minor modification that still makes the case for score, but
>> reduces the incentive for crowding strategy. And by restricting the number
>> of pairwise comparisons, it remains human countable and summable on the
>> second round (the pairwise part).
>>
>> On Tue, Jul 26, 2022, 17:30 Forest Simmons <forest.simmons21 at gmail.com>
>> wrote:
>>
>>> Might as well go all the way: while there are two or more uneliminated
>>> candidates, from among these remaining candidates eliminate the pairwise
>>> loser between the two with the lowest (remaining) scores.
>>>
>>> The entire finish order (if desired) can be obtained by bubble sorting
>>> the score order until no adjacent candidates are out-of-order pairwise.
>>> Rectification priority goes to the out-of-order adjacent pair whose
>>> pairwise loser has the lowest score.
>>>
>>> In fact, this method is identical to Ranked Pairs with lowest losing
>>> score corresponding to greatest defeat strength.
>>>
>>> The resulting full clone independence is well worth the tiny tweak of
>>> always starting at the bottom score candidate rather than the strangely
>>> arbitrary rule of starting at the third candidate from the top.
>>>
>>> El lun., 25 de jul. de 2022 9:28 p. m., Ted Stern <dodecatheon at gmail.com>
>>> escribió:
>>>
>>>> I was pointed to this voting simulator developed by Kyle Brockman that
>>>> contains a version of STAR3:
>>>>
>>>> https://www.chocolatepi.net/voteapp/
>>>>
>>>> In this model, STAR3 picks the top three scoring candidates, then the
>>>> winner is chosen by pairing S1 against the winner of S2 vs S3. Which is the
>>>> same as the Smith//Score winner for three candidates.
>>>>
>>>> This method has most of the features I look for:
>>>>
>>>> * More resistance to clones. Obviously, a crowding attack could still
>>>> work, but it's much less likely.
>>>>
>>>> * Some resistance to chicken dilemma. Not perfect, but enough to make
>>>> the strategy unpredictable.
>>>>
>>>> * Bias toward score winner.
>>>>
>>>> * Simplicity. As easy to describe as Vote321.
>>>>
>>>> On Wed, Jun 15, 2022, 12:56 Ted Stern <dodecatheon at gmail.com> wrote:
>>>>
>>>>> For my final (?) cloneproof STAR proposal, I think the virtual three
>>>>> candidate primary needs modification.
>>>>>
>>>>> If the first two candidates are the top two score winners, which third
>>>>> candidate would maximize equity in the
>>>>>
>>>>> That candidate can be found by, for each ballot, subtracting
>>>>> (ballot_score(score winner) + ballot_score(score runner up)/maxscore from
>>>>> the ballot's voting strength [or reducing voting strength to zero if that
>>>>> quantity is greater than 1], then finding the score winner over all
>>>>> reweighted ballots.
>>>>>
>>>>>
>>>>> This approach also minimizes pushover incentive.
>>>>>
>>>>> The goal here is to have at least 2 distinct factions represented in
>>>>> the extreme case where the top two scoresum candidates are clones.
>>>>>
>>>>> To test this, does anyone have any non-Smith STAR examples?
>>>>>
>>>>> On Tue, May 31, 2022, 11:29 Ted Stern <dodecatheon at gmail.com> wrote:
>>>>>
>>>>>> I've fleshed out a cloneproof STAR proposal using Score Sorted
>>>>>> Margins.
>>>>>>
>>>>>>    - Score ballots, 0-5
>>>>>>    - Aggregate total scores for all candidates.
>>>>>>    - We will find 3 primary winners. The first two are the
>>>>>>    candidates with top two score totals, Score winner (SW) and Score Runner-up
>>>>>>    (SRU)
>>>>>>    - The third primary winner, X, is found by reweighting each
>>>>>>    ballot according to its scores for SW and RU:
>>>>>>       - weight = 1 / (1 + (Ballot-Score[A] +
>>>>>>       Ballot-Score[B]/MaxScore)
>>>>>>       - and then re-summing total scores for reweighted ballots.
>>>>>>
>>>>>> The next round is decided using Score Sorted Margins. Using either
>>>>>> original scores, normalized scores, or scores in a separate runoff
>>>>>> election, sort the candidates SW, SRU and X in descending order of score.
>>>>>> If using the original scores, the ordering will be SW, SRU, X, but for
>>>>>> other cases, possibly not. Let's call that sorted ordering A, B, C for now.
>>>>>> The Score Sorted Margins winner for a 3 candidate case can be found as
>>>>>> follows:
>>>>>>
>>>>>>    - Find the three candidate score totals, sort them in descending
>>>>>>    order of score. We call the seeded order A, B, C.
>>>>>>    - Find the pairwise counts for A vs B, B vs C, and C vs A.
>>>>>>    - If there is a beats-all winner, that candidate is the winner.
>>>>>>    - Otherwise, if A>B, A wins
>>>>>>       - Why? Because there 8 possible cases (excluding ties) for the
>>>>>>       3 pairwise contests. 2 of those lead to A winning as CW, 2 lead to B as CW,
>>>>>>       and 2 to C as CW. The remaining cases are
>>>>>>       - A > B > C (> A), and
>>>>>>       - A < B < C (< A)
>>>>>>       - In the first cycle, the seeded ordering is already in
>>>>>>       pairwise sorted order, so the cycle is broken below C. So after filtering
>>>>>>       out CW cases, A>B determines we have the first cycle case.
>>>>>>    - Otherwise if margin(A,B) > margin(B,C), A wins
>>>>>>       - This is where a sorted margins iteration would actually take
>>>>>>       place -- both AvsB and BvsC are out of order pairwise. If the AB margin is
>>>>>>       greater, then the BC pair is swapped first, leading to a pairwise-sorted
>>>>>>       ordering of A > C > B.
>>>>>>    - Otherwise, B wins
>>>>>>
>>>>>> If the original Score order of candidates is preserved, then the
>>>>>> third primary candidate can only win if it's the Condorcet Winner. And the
>>>>>> runner up can win only if it's CW, or its margin with A is less than its
>>>>>> margin with C. So, overall, there is a bias toward the score winner.
>>>>>>
>>>>>> Personally, I would prefer a separate primary and runoff if there are
>>>>>> 4 or more candidates -- the primary has the effect of winnowing the field
>>>>>> and enabling closer scrutiny of candidates for the general election. If
>>>>>> there are only 2 or 3 candidates, a primary is unnecessary and you can go
>>>>>> straight to sorted margins for the general.
>>>>>>
>>>>>>
>>>>>> On Sun, May 29, 2022 at 11:56 AM Ted Stern <dodecatheon at gmail.com>
>>>>>> wrote:
>>>>>>
>>>>>>> Reviving an old topic.
>>>>>>>
>>>>>>> I had another thought for clone proofing STAR or Top Two Approval
>>>>>>> runoff, based on SPAV or RRV. It is not summable.
>>>>>>>
>>>>>>> Round one:
>>>>>>>
>>>>>>> Approval or Score ballots.
>>>>>>>
>>>>>>> Advance the top two approved or top two total score candidates.
>>>>>>>
>>>>>>> Advance a third candidate using SPAV with Approval ballots or RRV if
>>>>>>> score ballots, as if the two already advanced candidates were chosen by
>>>>>>> that method. That is, if using approval, a ballot's weight for the third
>>>>>>> count has weight 1 if it approved no previous winners, 1/2 if it approved
>>>>>>> one of the first two winners, or 1/3 if it approved both the previous
>>>>>>> winners. Similarly for score ballots using RRV.
>>>>>>>
>>>>>>> If round one uses Approval ballots, a score ballot runoff will be
>>>>>>> held. If using Score, the round one ballots can be recounted to find
>>>>>>> pairwise preferences, using ratings to infer rankings. Or a separate score
>>>>>>> runoff could also be held with the three winners, which I prefer.
>>>>>>>
>>>>>>> In round two, use a cloneproof and burial resistant Condorcet
>>>>>>> method. Let's say, score sorted margins or score chain climbing.
>>>>>>>
>>>>>>> The difference from my first proposal is that there are always 3
>>>>>>> candidates, representing either 2 factions, if top two are clones, or 3
>>>>>>> factions, if not cloned.
>>>>>>>
>>>>>>> My overall preference is for an approval first round, to eliminate
>>>>>>> most candidates, then the cloneproof third candidate will generally
>>>>>>> represent a different perspective to be debated before the runoff.
>>>>>>>
>>>>>>>
>>>>>>> On Sat, Mar 12, 2022, 00:17 Forest Simmons <
>>>>>>> forest.simmons21 at gmail.com> wrote:
>>>>>>>
>>>>>>>> Thanks, Kevin. It was a comment of yours that made me realize that
>>>>>>>> burial punishment (via chain climbing) was not enough ... but of course,
>>>>>>>> looking away and pretending the burier was probably sincere ... that is no
>>>>>>>> good either.
>>>>>>>>
>>>>>>>> So a sincerity check is natural ... if the sincere ballots
>>>>>>>> contradict the strategic ballots, then in this case you have both detection
>>>>>>>> and correction.
>>>>>>>>
>>>>>>>> Perhaps we could forget Chain Climbing and just use the sincerity
>>>>>>>> check on the weakest defeat that was critical in determining the winner.
>>>>>>>>
>>>>>>>> El vie., 11 de mar. de 2022 11:42 p. m., Kevin Venzke <
>>>>>>>> stepjak at yahoo.fr> escribió:
>>>>>>>>
>>>>>>>>> Hi Forest,
>>>>>>>>>
>>>>>>>>> Le vendredi 11 mars 2022, 23:03:30 UTC−6, Forest Simmons <
>>>>>>>>> forest.simmons21 at gmail.com> a écrit :
>>>>>>>>> > SCC:
>>>>>>>>> >
>>>>>>>>> > Initialize a variable X as the (name of) the lowest score
>>>>>>>>> candidate. Then ...
>>>>>>>>> >
>>>>>>>>> > While more than one candidate remains, eliminate all of the
>>>>>>>>> candidates pairwise
>>>>>>>>> > defeated by X, before storing a new name into X, the name of the
>>>>>>>>> lowest score
>>>>>>>>> > remaining candidate.
>>>>>>>>> > EndWhile
>>>>>>>>> >
>>>>>>>>> > The last value of X (the SCC winner Xf) is one of the finalists.
>>>>>>>>> >
>>>>>>>>> > The other finalist is the second to the last value of X, which
>>>>>>>>> we designate Xf'.
>>>>>>>>>
>>>>>>>>> For the case that the initial value of X is the CW, should an
>>>>>>>>> elimination order
>>>>>>>>> be specified?
>>>>>>>>>
>>>>>>>>> > But doesn't the last X defeat all of the previous X's?
>>>>>>>>> >
>>>>>>>>> > Yes, according to the ballots. But there is a good chance that
>>>>>>>>> the only reason
>>>>>>>>> > Xf defeats Xf' on the ballots is that Xf' was insincerely buried
>>>>>>>>> under Xf.
>>>>>>>>>
>>>>>>>>> In my terminology, that would mean Xf' is the sincere CW and Xf is
>>>>>>>>> the "pawn."
>>>>>>>>> The strategists' own candidate (the "rival") has been eliminated,
>>>>>>>>> so their
>>>>>>>>> strategy failed (and would be a backfire, if the last X simply
>>>>>>>>> won).
>>>>>>>>>
>>>>>>>>> This probably implies that the sincere CW was unexpectedly the
>>>>>>>>> Score loser.
>>>>>>>>>
>>>>>>>>> > So how do we vindicate (or expose as fraudulent) the finalist Xf?
>>>>>>>>> >
>>>>>>>>> > We could take another trip to the polls for a runoff between
>>>>>>>>> between Xf and Xf'.
>>>>>>>>> >
>>>>>>>>> > Otherwise, we can require voters to submit two ballots ... one
>>>>>>>>> to determine the
>>>>>>>>> > two finalists, and the other to choose between them.
>>>>>>>>> >
>>>>>>>>> > Sincere voters simply duplicate their first ballot to produce
>>>>>>>>> their second one.
>>>>>>>>> > The strategy burdened voters adjust their insincerities to
>>>>>>>>> produce their second
>>>>>>>>> > ballot.
>>>>>>>>> >
>>>>>>>>> > It is crucial that the second ballot be used exclusively for
>>>>>>>>> choosing the winner
>>>>>>>>> > between the two finalists.
>>>>>>>>> >
>>>>>>>>> > However, once the final winner has been certified , these
>>>>>>>>> ballots can be used
>>>>>>>>> > for forensics.
>>>>>>>>>
>>>>>>>>> All true. It seems like the effect of this is to make "backfired
>>>>>>>>> strategy"
>>>>>>>>> outcomes impossible. Is that the goal? It seems like that might
>>>>>>>>> risk encouraging
>>>>>>>>> voters to *try* burial strategies, unless it's sufficient to "name
>>>>>>>>> and shame"
>>>>>>>>> strategists through the forensics performed afterwards.
>>>>>>>>>
>>>>>>>>> It seems like this proposal could even prevent a backfire when
>>>>>>>>> *both* of two
>>>>>>>>> major factions are ranking the same pawn insincerely high, so that
>>>>>>>>> the pawn
>>>>>>>>> becomes the voted CW.
>>>>>>>>>
>>>>>>>>> Kevin
>>>>>>>>>
>>>>>>>> ----
>>>>> Election-Methods mailing list - see https://electorama.com/em for
>>>>> list info
>>>>>
>>>>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.electorama.com/pipermail/election-methods-electorama.com/attachments/20220727/2cb0a332/attachment-0001.htm>