[EM] Holy grail: PAR with FBC?

[Kevin Venzke]

Hi Jameson,
Except for a couple of details I have a method like this on the wiki (called CdlA). The differences are that I don't have step 2 at all, and in step 4 instead of "don't prefer the leader" I have "reject the leader."
Under my method, FBC is violated because if my favorite happens to become a tally leader, this could cause other voters, who reject my favorite, to provide additional preferences that I may not myself like. (Whereas, if I had not top-rated my favorite, the other voters' preferences may have stayed concealed.) Generally speaking we have to guarantee that raising a favorite to equal-top won't change the winner unless it makes the favorite win. Alternatives are possible, but we would have to be extremely careful in how we use the information.
I believe under your method, the only time a voter doesn't eventually upgrade his "accepts" into "prefers" is if he prefers every tally leader that ever comes up. I guess most of the time, accepts and prefers end up counting the same. But the concern would be that there are ballots out there that prefer all the tally leaders (including my compromise choice, but excluding my favorite) and accept some candidates worse than my compromise. In that case I could regret voting for my favorite because of how it affects the influence contributed by other voters.
I tend to appreciate methods along these lines, though, because they emulate, to some extent, a realistic process of group decision making.
Kevin

      De : Jameson Quinn <jameson.quinn at gmail.com>
 À : electionsciencefoundation <electionscience at googlegroups.com>; EM <election-methods at lists.electorama.com> 
 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". Meanwhile, the system below is temporarily called PARFBC.    
   - Voters can Prefer, Accept, or Reject each candidate. Default is Accept.
   - Candidates with a majority of Reject, or with under 25% Prefer, are eliminated, unless that would eliminate all candidates.
   - Tally "prefer" ratings for all non-eliminated candidates.
   - 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).
   - Repeat step 4 until the leader doesn't change. The winner is the final leader.

...
This is pretty much a holy grail system from my perspective. It meets FBC (I think; I don't have a proof, but it seems to me it should). It deals with a simple chicken dilemma without a slippery slope. It deals with center squeeze with naive ballots. I think it even meets the voted majority Condorcet criterion, in an election with 3 candidates and where all ballots use the full range (and you can add irrelevant "also-rans" to such an election without breaking any compliances).
It has a sequential counting process like IRV, and so it fails summability; but in most cases, step 4 will not change the outcome, so will happen only once. (The main exception is if there's a voted Condorcet cycle.)
It even meets weakened versions of both Later No Help and Later No Harm; weak enough so that they are compatible with the above passed criteria, but strong enough so that I think most voters would be honest. Later No Help holds if there's no possible Condorcet cycle; and Later No Harm holds if the "later" candidate isn't on the edge of being eliminated.
I think that the explanation is clear and intuitive enough to be reasonably acceptable to most voters. It involves only simple adding to tallies, not anything couched in terms of sets or multiplication or the like.
Does anybody have any reason why this system should not be considered a leading contender for "next step after approval"?
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