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

[C.Benham]

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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