[EM] Smith//MMPO

[Michael Ossipoff]

I at first didn't realize that this message was sent to EM. So that's why
this reply is so late.

On Sep 27, 2016 7:21 AM, "C.Benham" <cbenham at adam.com.au> wrote:
>
> Mike,
>
> Your "MAM-like strategy" example:
>
> 30: A  (sincere may be A>B)
>
> 20: B>A
> 25: C>B
>
> And you are happy that WV and Smith//MMPO  elects B  (the supposed/maybe
"sincere CW").

(endquote)

Voters will do what it takes, to elect a candidate whom they perceive as
the CWs (sincere CW).

Making that as easy as possible has been the appeal of wv.

> But  WV  (including MAM) and  Smith//MMPO both have a random-fill
incentive. From a recent email:
>
>>  C: If the method has a random-fill incentive then it is more logical to
assume that truncators are more sincere than those
>> who rank more candidates.
>>
>>  M: True.

But strategic truncation can take the win away from the CWs.

>>
>
> Therefore any assumption that B is the "sincere CW" has a very flimsy
basis.

(endquote)

As I said above, voters will do what it takes to elect a candidate whom
they perceive as a CWs.

Making that as easy as possible has been the appeal of wv.

The message continued:

A, being positionally dominant (if these are 3-slot
> ratings ballots...

wv & MMPO are intended for unlimited rankings.

...then A is the most Top-Rated and the most Approved) and uncovered is
arguably the prettiest winner.  Most likely
> there is no "sincere CW"  and  A is the highest Social Utility candidate.

(endquote)

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).

The message continued:

> In any case under WV and  Smith//MMPO  the A supporters can make A the
winner by voting A>C.

(endquote)

Yes, that's why the B voters should plump if they feel that B is likely to
be a CWs.

If the CWs's voters plump, in WV or MMPO, that thwarts & penalizes burial.

The message continued:

I don't think that "thwarting"
> a bad "strategy" that is probably sincere or not very insincere at the
cost of allowing a more insincere strategy to work fine is
> any achievement.

(endquote)

The purpose is just to minimize the strategy needs of voters trying to
protect a perceived CWs.

I don't have a way to delete text. I reply farther down:

...as voters will do.
> 30: A>C
>
> 20: B>A
> 25: C>B
>
> B>A 45-30,     A>C 50-25,    C>B 55-20.    Max PO scores:  A45 < C50 <B55.
>
> A method that I like that does elect B in your example is Approval Sorted
Margins.

Interestingly, ASM seems (at 1st examination at least) to have wv-like
strategy, without wv's bottom-end burial-incentive.

If so, that means that, in a strategically-voted election, ASM retains wv's
advantages better than wv would.

Michael Ossipoff

>
> http://wiki.electorama.com/wiki/Approval_Sorted_Margins
>
> It initially orders the candidates from most approved to least approved.
If any adjacent pair is out of order pairwise
> it switches the order of the pair with the smallest difference in their
approval scores. If there is a tie for that it switches
> the tied pair lowest in the order.  At the end of the process it elects
the highest-ordered candidate.
>
> The method meets Plurality and Minimal Defense and fails Weak CD. In the
second example (with 30 A>C) it narrowly elects C:
>
> Approval scores:  C55 > A50 > B45.   Both C>A and  A>B are pairwise out
of order and in both cases the difference in approval scores
> is 5, so we switch the lower-ordered of the two pairs to give C>B>A. Now
no adjacent pair is pairwise out of order so that order is final
> and C wins.
>
> Chris Benham
>
>
>
>
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