[EM] FBC, center squeeze, and CD

[Jameson Quinn]

I earlier said that C would win in "PARFBC" in Chris's scenario. I was
wrong, as Chris nicely pointed out to me privately:


43: A
03: A>B
44: B>C
10: C

C is eliminated for having under 25% prefer, and so A wins.

Honestly, I think that a scenario where the approval winner is eliminated
on this basis is not very plausible. If 15 of the B>C voters switched to
BC, then C would win. This switch would not stop B from winning if there
were more A>B voters, so it's strategically safe; it's not hard to imagine
that 1/3 of the honest B>C>A voters might vote like that either naively or
strategically.

2016-11-09 10:09 GMT-05:00 C.Benham <cbenham at adam.com.au>:

> *Envoyé le :* Lundi 7 novembre 2016 8h27
> *Objet :* [EM] Holy grail: PAR with FBC?
>
> Here's a new system. It's like PAR, but meets FBC, and deals with center
> squeeze correctly in the few tricky cases where PAR doesn't. I'm
> considering using the PAR name for this system, and renaming the current
> PAR to something like "Old Par
> <http://sr3.wine-searcher.net/images/labels/29/06/grand-old-parr-12-year-old-blended-scotch-whisky-scotland-10152906t.jpg>".
> Meanwhile, the system below is temporarily called PARFBC
> <http://wiki.electorama.com/wiki/PARFBC_voting>.
>
>
>    1. Voters can Prefer, Accept, or Reject each candidate. Default is
>    Accept.
>    2. Candidates with a majority of Reject, or with under 25% Prefer, are
>    eliminated, unless that would eliminate all candidates.
>    3. Tally "prefer" ratings for all non-eliminated candidates.
>    4. Find the leader in this tally, and add in "accept" ratings on
>    ballots that don't prefer the leader (if they haven't already been tallied).
>    5. Repeat step 4 until the leader doesn't change. The winner is the
>    final leader.
>
>
>
> 43: A
> 03: A>B
> 44: B>C
> 10: C
>
> No, PARHG (PAR Holy Grail) elects C here.
>
>
> With default being "Accept", no candidate has a  "majority of Reject" but
> C has  "under 25% Prefer" so is eliminated under rule 2. Then I suppose A
> wins.
>
> If we assume that the truncators  are giving "Rejects" to the
> unrated/unranked candidates, then I suppose both A and B have a "majority
> of Rejects" and so
> none of the candidates are eliminated and then as you say C would win. (My
> mistake was that I didn't notice B's "majority of Reject" so I thought that
> C and
> A would be eliminated).
>
> Have I now got this right?  If so I'll correct my mistake on EM.
>
> Chris
>
> On 11/9/2016 5:07 PM, Jameson Quinn wrote:
>
>
>
> 2016-11-08 23:25 GMT-05:00 C.Benham <cbenham at adam.com.au>:
>
>> On 11/9/2016 8:35 AM, Michael Ossipoff wrote:
>>
>> (You wrote) :
>>
>> And it isn't clear to me that "wv-like strategy" is even something we
>> should take if it was free.
>>
>> (endquote)
>>
>> In Benham, Woodall, ICT, & probably many or most pairwise-count methods,
>> the CWs has no protection from burial, or even from innocent, non-strategic
>> truncation.
>>
>> With wv-like strategy, truncation from one side can't take victory from
>> the CWs & give it to the truncators' candidate.
>>
>> ...and plumping by the CWs's voters makes it impossible for burial to
>> succeed. In fact, the mere threat of that plumping can deter burial.
>>
>>
>> So to "protect"  some candidate  that some voters imagine is the sincere
>> CW (when perhaps there is no sincere CW or some other candidate
>> is the sincere CW) you want to have a "defensive truncation" strategy
>> available* inside* a method with a very strong random-fill incentive?
>>
>> And you should add (and stress) that it needs plumping by *all  *of the
>> "CWs voters to make it impossible for burial to succeed", and not ,say,
>> merely 93% of them (with the other 7% sincerely fully ranking):
>>
>> 43: A
>> 03: A>B
>> 44: B>C  (sincere may be B or B>A)
>> 10: C
>>
>> 100 ballots.  C>A 54-46,   A>B 46-44,  B>C 47-10.   Top Ratings A46 > B44
>> > C10.   Approvals: C54 > A46 > B44.
>>
>> Here MDDTR  (like MDDTA and WV and Margins and MMPO and Jameson's latest
>> "holy grail")  all elect the possibly burying voters' favourite, B.
>>
>
> No, PARHG (PAR Holy Grail) elects C here.
>
>
>>
>> Viewing the ballots from the top, A is the strongest candidate (and
>> possibly the sincere CW) and viewing the ballots from the bottom C is the
>> strongest candidate.  And electing B is simply a very bad (and flagrant)
>> failure of  Later-no-Help. And B is both pairwise beaten and positionally
>> dominated by A.
>>
>> So I can't accept any method that in this scenario elects B.
>>
>> Chris Benham
>>
>>
>>
>>
>>
>>
>>
>> ----
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>> info
>>
>>
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