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Technical discussion of election methods

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Still looking for a simple system: PAR?

JQ
Jameson Quinn
Wed, Nov 2, 2016 11:31 AM

I've been talking about MAS (aka U/P, etc) and MSV for some time now. The
idea is to have an FBC-compliant system that's easy to describe and that
handles both chicken dilemma (primarily by avoiding the slippery slope, not
by punishing defectors unless their faction is under 25%) and center
squeeze (ideally, without requiring truncation). Both MAS and MSV were
designed so that even if a large number (say, 51%) of voters are lazy,
using the default for all but their favorite and least-favorite, the
chicken dilemma and center squeeze are still workable.

This is a hard problem, and I'm still not fully satisfied with either MAS
or MSV. MAS has too-complicated a default rule; and MSV has 4 ratings when
only 3 of them are strategically ideal for any given voting faction. Both
of these problems come from the same source: the things that help with CD
tend to be a problem with center squeeze and vice versa.

So, let me try yet again. Here's a new idea, using an optional SODA-like
logic to deal with center squeeze:

  • Candidates can optionally designate some subset of the other
    candidates as "preferable" (as compared to those not in the subset). This
    information is included on or with the ballot.
  • 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.
  • For each non-eliminated candidate X, tally the number of "prefers",
    plus the number of ballots that accept X and prefer only eliminated
    candidates who found X "preferable". Highest tally wins.

Hmm. No. This proposal is obviously harder to explain than either MAS or
MSV. Yes, it deals with center squeeze better than the former, and has a
simpler ballot than the latter. But it doesn't really have any advantages
at all over MSDSV.

Here's MSDSV again:

  • 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.
  • The winner is the non-eliminated candidate rated equal-or-above any
    other non-eliminated candidate on the most ballots.

This is a solid system, and the above description avoids the problems with
my original formulation involving changing ballots. Perhaps it could be
called PAR voting, after the rating categories.

Its greatest problem is the lack of simple summability. Still, if you allow
for two-pass counting (first, find which candidates are eliminated; then,
once that's known, count ballots again to find the tally for each
non-eliminated candidate), that's resolvable.

I think I'm favoring this system over MAS or MSV. I guess I should make it
a page on the wiki...

I've been talking about MAS (aka U/P, etc) and MSV for some time now. The idea is to have an FBC-compliant system that's easy to describe and that handles both chicken dilemma (primarily by avoiding the slippery slope, not by punishing defectors unless their faction is under 25%) and center squeeze (ideally, without requiring truncation). Both MAS and MSV were designed so that even if a large number (say, 51%) of voters are lazy, using the default for all but their favorite and least-favorite, the chicken dilemma and center squeeze are still workable. This is a hard problem, and I'm still not fully satisfied with either MAS or MSV. MAS has too-complicated a default rule; and MSV has 4 ratings when only 3 of them are strategically ideal for any given voting faction. Both of these problems come from the same source: the things that help with CD tend to be a problem with center squeeze and vice versa. So, let me try yet again. Here's a new idea, using an optional SODA-like logic to deal with center squeeze: - Candidates can optionally designate some subset of the other candidates as "preferable" (as compared to those not in the subset). This information is included on or with the ballot. - 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. - For each non-eliminated candidate X, tally the number of "prefers", plus the number of ballots that accept X and prefer only eliminated candidates who found X "preferable". Highest tally wins. Hmm. No. This proposal is obviously harder to explain than either MAS or MSV. Yes, it deals with center squeeze better than the former, and has a simpler ballot than the latter. But it doesn't really have any advantages at all over MSDSV. Here's MSDSV again: - 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. - The winner is the non-eliminated candidate rated equal-or-above any other non-eliminated candidate on the most ballots. This is a solid system, and the above description avoids the problems with my original formulation involving changing ballots. Perhaps it could be called PAR voting, after the rating categories. Its greatest problem is the lack of simple summability. Still, if you allow for two-pass counting (first, find which candidates are eliminated; then, once that's known, count ballots again to find the tally for each non-eliminated candidate), that's resolvable. I think I'm favoring this system over MAS or MSV. I guess I should make it a page on the wiki...