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Re: [EM] FBC, center squeeze, and CD

JQ
Jameson Quinn
Wed, Nov 9, 2016 6:16 PM

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@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@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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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@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@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 >> >> >> >> >> >> >> >> ---- >> Election-Methods mailing list - see http://electorama.com/em for list >> info >> >> > No virus found in this message. > Checked by AVG - www.avg.com > Version: 2016.0.7859 / Virus Database: 4664/13373 - Release Date: 11/08/16 > > >