[EM] SARA voting: easier-to-describe MAS

C.Benham cbenham at adam.com.au
Tue Oct 25 19:48:16 PDT 2016


You mean "disqualified"  like all other Condorcet  methods?

Chris Benham


On 10/26/2016 9:05 AM, Michael Ossipoff wrote:
> Oops! Smith//Approval is disqualified by its FBC failure
>
> Michael Ossipoff
>
> On Tue, Oct 25, 2016 at 2:55 PM, Michael Ossipoff 
> <email9648742 at gmail.com <mailto:email9648742 at gmail.com>> wrote:
>
>     But MMPO's Weak CD remains as an advantage, because the chicken
>     dilemma can be a nuisance in Approval.
>
>     So MMPO isn't completely ruled out.
>
>     Michael Ossipoff
>
>     On Oct 25, 2016 9:40 AM, "C.Benham" <cbenham at adam.com.au
>     <mailto:cbenham at adam.com.au>> wrote:
>
>         On 10/25/2016 4:47 AM, Michael Ossipoff wrote:
>
>>         When sincerely-voted Approval chooses differently from
>>         Condorcet, it's choosing socially better.
>>
>>         (Jameson wrote):
>>
>>         But even if they do win under honesty, they will probably
>>         lose under "semi-honest offensive strategy" (SHOS) in which
>>         the stronger wing truncates the CW to equal-bottom.
>>
>>         (endquote)
>>
>>         In rank methods, we've been calling that offensive truncation.
>>
>>         In Approval, I don't regard it as an offensive strategy at
>>         all. In Approval, the middle CWs doesn't need support from
>>         both sides, as s/he does in general pairwise-count methods.
>>
>>         The larger wing isn't the one that needs the CWs, if you're
>>         after the best particular candidate you can get. But you're
>>         talking about a strategy problem that shouldn't concern
>>         voters in Approval.
>>
>
>         Mike,
>
>         Given my selection of quotes above, I find your negativity on
>         Smith//Approval  (very similar to Max Covered Approval) a bit
>         inconsistent.
>
>         A couple of somewhat relevant questions:
>
>         (1)How often is a sincere Condorcet winner who is supported by
>         the smallest of three factions of voters the Approval winner?
>
>         (2) How often is the Approval winner not in the Smith set?
>
>         And so what is wrong with Condorcet//Approval?
>
>>         Jameson:-In Condorcet systems, the CW wins under honesty by
>>         definition. But under SHOS, any CD-compliant method gets the
>>         wrong answer.
>>
>>         Mike: No. In wv, a CWs isn't vulnerable to truncation. S/he
>>         still wins. ...the right answer in such a method.
>>
>
>          But Winning Votes isn't a "CD-compliant method" .
>
>         Jameson wrote:
>
>>         Support Accept Reject Abstain voting works as follows:
>>
>>           * Voters can support, accept, reject, or abstain on each
>>             candidate. Default is abstain.
>>           * Call a candidate "acceptable" if they are rejected by 50%
>>             or less and supported or accepted by over 25%. If any
>>             candidates are acceptable, eliminate all who aren't.
>>           * Give remaining candidates 2 points for each "support", 1
>>             point for each "accept", and half a point for each
>>             "abstain". Highest points wins.
>>
>>
>         I still hate default being anything other than
>         bottom/"reject", and the "25%" figure looks arbitrary.
>
>         With the default rule as it is, it looks like the method fails
>         Mono-add-Plump.
>
>         Say the winner X has a lower point score than some other
>         candidate Y that is barely rejected by over 50%. Then adding
>         some ballots that do nothing
>         but "support" X could raise the 50% threshold enough so that
>         now Y is no longer eliminated and wins.
>
>         Chris Benham
>
>
>>
>>         On Oct 23, 2016 8:21 AM, "Jameson Quinn"
>>         <jameson.quinn at gmail.com <mailto:jameson.quinn at gmail.com>> wrote:
>>         >
>>         > Center squeeze occurs in 3-candidate election when the CW
>>         is the plurality loser.
>>
>>         So it refers to a special case of the problem of the
>>         defensive strategy needed to protect the CWs's win.
>>
>>         Certainly, in IRV, Benham, & Woodall, the main problem is
>>         when a middle Cws has the smallest faction.
>>
>>         And, in other pairwise-count methods, when I test for
>>         truncation or burial vulnerability, I use such an example,
>>         because it seems more favorable to finding vulnerability.
>>
>>         But a CWs can lose without being smallest, and I don't make a
>>         distinction about that except that it's part of the
>>         problem-examples in IRV, Benham, and Woodall.
>>
>>         You wrote:
>>
>>         There are different levels of the problem, characterized by
>>         the level of strategy necessary for the CW to win:
>>
>>         (endquote)
>>
>>         Sure. I was saying that with wv strategy, truncation from one
>>         side can't take the win from the CWs. ...& that the CWs's
>>         voters can deter burial by mere plumping.
>>
>>         No need for the non-offensive wing to vote any less than
>>         sincerely in methods with wv strategy.
>>
>>         As you know, that isn't so with other Condorcet versions or
>>         general pairwise-count methods.
>>
>>         (You wrote):
>>
>>         >
>>         > -In systems like IRV or plurality, in order for the CW to
>>         win even under honesty, the weaker of the two wings must
>>         betray their sincere favorite.
>>
>>         (endquote)
>>
>>         Well, it isn't so much the size of the wing factions. It's
>>         more a matter of which wing candidate is preferred by the
>>         CWs's voters.
>>
>>         That's why I've been saying that IRV is fine for you if
>>         you're majority-favored.
>>
>>         If the CWs's voters transfer the other way, then you aren't
>>         in a mutual-majority, and then, for you, IRV is then no
>>         better than Plurality.
>>
>>         Many of us have been explaining that to Rob Richie for the
>>         past 30 years or so.
>>
>>         > -In systems like approval and score, the CW may or may not
>>         win under "honesty" (however defined). Arguably, if they do
>>         not, they should not.
>>
>>         (endquote)
>>
>>         Correct. When sincerely-voted Approval chooses differently
>>         from Condorcet, it's choosing socially better.
>>
>>         Sure, not choosing the CWs got IRV repealed in Burlington.
>>
>>         Not electing the CWs results in a majority who'd prefer a
>>         different result.
>>
>>         But I think IRV was repealed for more than that:
>>
>>         Approval let's people protect the CWs, without
>>         favorite-burial,  if that were what they want to do.  ...and
>>         I suggest that it isn't, because electing from your top-set
>>         is usually more important than electing the best particular
>>         individual candidate you can.
>>
>>         CWs protection is more for rank methods, which are about
>>         choosing _among_ your top-set, to elect the best particular
>>         candidate you can.
>>
>>         (But see my earlier post yesterday, about that.)
>>
>>         If you have a top-set, then, by definition, electing from it
>>         is the important thing.
>>
>>         Approve (only) your top-set.
>>
>>         (More about that in my post yesterday)
>>
>>         But, if it turned out to be really important to avoid having
>>         a majority who'd prefer a different result, then that  could
>>         be a reason for voters in Approval to slightly modify their
>>         voting to avoid approving past the expected CWs (CWse).
>>         ...though that would lower your Pt.
>>
>>         When approving your top-set, you'd just stop short of
>>         approving past the CWse.
>>
>>         Yesterday, too, I spoke of the possibility of your
>>         wing-faction having a social agreement to that effect.
>>
>>         What you're saying doesn't contract what I've been saying.
>>
>>         (You wrote):
>>
>>         But even if they do win under honesty, they will probably
>>         lose under "semi-honest offensive strategy" (SHOS) in which
>>         the stronger wing truncates the CW to equal-bottom.
>>
>>         (endquote)
>>
>>         In rank methods, we've been calling that offensive truncation.
>>
>>         In Approval, I don't regard it as an offensive strategy at
>>         all. In Approval, the middle CWs doesn't need support from
>>         both sides, as s/he does in general pairwise-count methods.
>>
>>         The larger wing isn't the one that needs the CWs, if you're
>>         after the best particular candidate you can get. But you're
>>         talking about a strategy problem that shouldn't concern
>>         voters in Approval.
>>
>>         (You wrote):
>>
>>         The defensive strategies that work are for the weaker wing to
>>         give the CW near-top score, and/or the CW faction to give the
>>         stronger wing near-bottom score.
>>
>>         (endquote)
>>
>>         Both, if people are trying for the best candidate they can
>>         get. Then obviously the smaller wing should support the CWs,
>>         and the CWs's voters should plump.
>>
>>         But I don't suggest that goal for Approval, for the reasons
>>         stated above, & in earlier posts.
>>
>>         > -In Condorcet systems, the CW wins under honesty by
>>         definition. But under SHOS, any CD-compliant method gets the
>>         wrong answer.
>>
>>         No. In wv, a CWs isn't vulnerable to truncation. S/he still
>>         wins. ...the right answer in such a method.
>>
>>         With burial, a potentially successful buial can succeed or
>>         fail, depending on whether the CWs's voters plump. Either
>>         way, the CWs doesn't win.
>>
>>         (You wrote):
>>
>>         ; the strategy is effective if the CW faction plumps, and
>>         backfires if the CW faction cooperates with the weaker wing.
>>         Note that even a strategy backfire here is not in my opinion
>>         a "good" result; because the strategy has some chance of
>>         winning, it will be sometimes attempted. Strategic backfire
>>         is a good thing if it discourages the strategy, but a bad
>>         thing if it actually occurs.
>>
>>         Yes, that's what makes Condorcet at least a bit questionable.
>>         ...especially with the possibility of the perpetual burial
>>         fiasco.
>>
>>         But it can probably be argued that, with rank methods' goal
>>         of getting the best individual candidate you can get, wv
>>         strategy improves on Bucklin, because, even if people
>>         misjudge who the CWs is, and so hir voters don't plump, the
>>         mere threat of plumping could be enough to deter burial,
>>         because the would-be buriers don't have better information
>>         than the defenders have.
>>
>>         > -In most basic Bucklin systems, the CW faction must
>>         defensively plump to counteract SHOS.
>>
>>         Yes, in Bucklin, if you aren't majority-favored, and if you
>>         rank sincerely, and if the CWs's voters don't plump, then
>>         that can result in the election of someone in your bottom-set.
>>
>>         (You wrote):
>>
>>         > -In a system like SARA, in most cases, even if the CW does
>>         not defensively plump, the weaker wing can give enough
>>         support to the CW to protect them from SHOS, without having
>>         to rate them equal-top. (If the CW is only barely a CW, the
>>         weak wing may have to rate equal-top for a successful defense
>>         in this case. However, I think that very tightly-balanced
>>         situations like this are not a large concern.)
>>
>>         (endquote)
>>
>>         That makes me sit up & take notice, because such an
>>         improvement on Bucklin strategy, while keeping FBC, would be
>>         major, & could outweigh the lack of CD enough to compete with
>>         the best methods.
>>
>>         Michael Ossipoff
>>
>>
>
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