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

[Michael Ossipoff]

On Oct 23, 2016 8:21 AM, "Jameson Quinn" <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Sure, not choosing the CWs got IRV repealed in Burlington.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But I think IRV was repealed for more than that: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

>
>
>
> 2016-10-23 10:05 GMT-04:00 Michael Ossipoff <email9648742 at gmail.com>:
>>
>> Could you give a brief, precise definition of center squeeze?
>>
>> Michael Ossipoff
>>
>> On Oct 22, 2016 3:24 PM, "Jameson Quinn" <jameson.quinn at gmail.com> 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.
>>>
>>> This moves a bit away from the Bucklin roots of MAS, but it further
reduces the instability of cooperation in a CD scenario.
>>>
>>> ----
>>> Election-Methods mailing list - see http://electorama.com/em for list
info
>>>
>>
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>>
>
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