[EM] Smith//MMPO

[Michael Ossipoff]

On Sep 29, 2016 11:48 AM, "C.Benham" <cbenham at adam.com.au> wrote:
>
> Mike,
>
> The example we are discussing:
>
>
> 30: A  (sincere may be A>B)
> 20: B>A
> 25: C>B
>
> You like that Winning Votes and Smith//MMPO  elects B.

Yes.

>
> On 9/29/2016 12:49 AM, Michael Ossipoff wrote:
>
>> Voters will do what it takes, to elect a candidate whom they perceive
as the CWs (sincere CW).
>
>
> C:   How do you know that?

That's typically the best they can get.

(You wrote) :

 Won't they  (at least also) try to elect candidates they prefer to their
perceived "sincere CW"?

(endquote)

Sure, it's a fair assumption that people who rank want to rank in sincere
order for that reason.

I won't approve the expected CWs (CWse) if s/he's bottom-set. (Maybe I'd
rank hir in MMPO). So if some others feel similarly, that's an exception to
helping the CWse. I don't know how many agree. It would complicate the
examples.

> If you are right, then presumably in our example the 3 factions of voters
all have different "perceived sincere CWs" because
> they voted for different candidates.

The assumption is that the A voters truncate because they want to make  A
win instead of the CWse, or that it's lazy or principled truncation.

The C voters rank B over C, helping the CWse.

I think it's a good presumption that all perceive the same CWse, because
the same information is available to all.

(I'd said) :

>> Natural, non-strategic, top-cycles are vanishingly rare in political
polls. At CIVS (Condorcet Internet Voting Service) I'm not aware of there
ever having been a top-cycle for top-finisher.
>>
>> So. Most likely there _is_ a CWs (sincere CW).
>>
>
> C: That isn't rational.

How so?

(You wrote) :

Presumably a  ballot set like our example, with 30 A or 30 A>C  is also
vanishingly rare.

(endquote)

Yes, if it is a sincere cycle. But otherwise no.

(You wrote) :

The question isn't how rare top-cycles in general are.
> The question is how reasonable is to assume that the A truncators in this
particular example are insincere.
(endquote)

The rarity of sincere top cycles is highly relevant to the matter of this
cycle's sincere-ness.

The A voters could prefer B to C, but do principled or strategic truncation.

B would then still be CWs.

(You wrote) :

> In essence an election method should aim to achieve just two things:
maximise probable Social Utility and minimise possible voter regret.  If
fulfilling those aims
> is done without electing some candidate that someone imagines is the
"sincere CW", then that isn't a problem.

(endquote)

That's a matter of individual preference. I prefer making easy for those
wanting to protect a perceived CWs. You want to maximize SU. Neither goal
is wrong.

BTW, if distance in issue-space is measured by city-block distance, then
the CWs is the SU maximizer.

...& there's good justification for city block distance.

But SU is of doubtful importance. Greater disutilities are more important
to reduce than smaller ones. Is giving a dollar to a millionaire really as
good as giving it to a homeless person? (or giving the millionaire some
larger amount that has equal utility to him)

> In the example there is no compelling rational reason to assume that any
of the ballots are insincere.  So there is no "sincere CW".

1.Sincere top cycles are evidently vanishingly rare.

2. It's good to minimize the strategic insincerity needed by someone who
wants to protect a perceived CWs.

(I'm not saying that other goals are wrong.)

> A, as an uncovered positionally dominant candidate is presumably the
highest SU candidate.

A perfectly valid goal. But the CWs is a likely SU maximizer.

(Replying farther down)

(You wrote) :

(All the Condorcet methods I currently advocate would elect A).
>
> So say we elect A.  In that case the 25 C>B voters might regret not
making their second-choice win (in any Condorcet method) by voting C=B (or
B>C or B).
>
> But say instead  Winning Votes or  Smith//MMPO is used and we elect B.
In that case the 30 A voters would regret not causing their favourite to
win by
> voting A>C.

That wouldn't have worked, if the B voters defensively plumped. The A
voters would be taking a big risk.

>
> And that clinches the case for any good method that elects A versus any
method that elects B with the 30 A voters truncating, and A when they vote
A>C.

Depends on one's goal.

>
> Approval Sorted Margins isn't as bad because under it if the A supporters
vote A>C it results in C winning.
(endquote)

If B voters plump, wv does the same.

>Also it meets mono-switch->plump and of course
> (since above-bottom ranking is interpreted as approval) has some
truncation incentive.

ASM is worth checking out. A disadvantage is that principled truncation of
the CWs is more likely to defeat the CWs & elect someone whom the
truncators dislike more.

Michael Ossipoff
> Chris  Benham
>
>
>
>
>
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