[EM] MAM vs Schulze

[Michael Ossipoff]

On Oct 8, 2016 6:06 AM, "C.Benham" <cbenham at adam.com.au> wrote:
>
> Mike,
>
> As far as I can tell, for all intents and purposes  MAM,  Schulze, River
and  Smith//MinMax (wv)  are all just different wordings
> of the same method.

No. They sometimes choose different winners.
>
> If you think that MAM  is better than Shulze, then what criterion (that
we might care about) is met by MAM and not Shulze?

Sometimes they choose the same, sometimes they don't.

When they don't, the MAM winner is publicly preferred to the Schulze winner
several times more often than vice-versa.

(It seems to me that it might have been something like 4 to 1, or 5 to 1.
Steve Eppley would be the one to ask.)

So: Choose in keeping with public preference, or contrary to it. Your choice

MAM's brief, natural & obvious definition is the opposite of the arbitrary
definition of Schulze or CSSD.

MAM's definition clearly is the one that doesn't unnecessarily disregard a
defeat.

It disregards a defeat only it's the weakest in a cycle with defeats for
which there  _isn't_
justification to disregard them.

And, as I said, it's no surprise when unnecessarily disregarding defeats
results in a winner to whom the public prefer the MAM winner.

>
> Or perhaps you have some example in mind where you think the MAM winner
is much prettier than the Schulze  winner?

Publicly-preferred is prettier.

Minimally disregarding defeats only with obviousl, strong justification,
never unnecessarily disregarding a defeat--That's prettier.

>
>
>> MAM's brief definition just says:
>>
>> A defeat is affirmed if it isn't the weakest defeat in a cycle whose
other defeats are affirmed.
>>
>
> C: Is that definition fully adequate?

Yes.

You wrote:

It doesn't tell you where to start.
>

It isn't a procedural definition or a count-instruction. It's a brief
recursive definition.

Given a set of rankings, it fully and definitely specifies a set of
affirmed defeats, & a set of not-affirmed defeats.

...and fully specifies the winner.

For a procedure:

Write down the strongest defeat.

Below it, write down the next strongest defeat.

Below that, write down the next strongest defeat, if it doesn't cycle with
defeats already written down.

Repeat the paragraph before this one, until all the defeats have been
considered as described in that paragraph.

A candidate wins if s/he has no written-down defeats.

(end of count instruction)

>> So, if it will be rare for them to differ, does that mean that we should
propose the more complicatedly-worded, elaborately- worded one?
>>
>> ...the less obviously, naturally and clearly motivated & justified one?
>>
>
> C: Recently you accepted that  Winning Votes  is at best "maybe a bit
questionable", so why do you think that we should "propose" either?

(endquote)

I said they might be iffy or questionable. I didn't say they're ruled out.

For that questionable-ness, you get a chance for much better strategy.

...at the cost of the possibility of the strategic mess of the
perpetual-burial fiasco.

I'd say that MAM, Smith//MMPO, & plain MMPO are worth a try.

They should be included in a proposal that lists a number of suggested
methods.

In particular, for an unlimited-rankings method, Plain MMPO offers the
most, for current conditions.

>
> If  you want a Condorcet method that meets  Chicken Dilemma then I prefer
both "Benham"  and  Losing Votes (erw) Sorted Margins Elimination.

(endquote)

They're far too vulnerable to truncation & burial.

In WV & MMPO, truncation just doesn't work. The CWs still wins.

The strategy situation of the methods you listed isn't as good as Bucklin.

Surely the purpose of a pairwise-count method is to _improve_ on Bucklin.

In Bucklin & Approval, the CWs's preferrers can protect hir win by plumping.

In Benham, Woodall, & Margins-Sorted LV Elimination, the best they can do
is:

Say it's Worst (W), Middle (M), & Favorite (F).

M is the middle CWs.

The M voters could estimate or look up the expected sizes of the W & F
factions.  ...& rank one over the other probabilistically, so that each
one's probability of pair-beating the other is 50%.

...so that burial has a 50% chance of backfiring.

In Bucklin, WV or MMPO, they need merely to plump.

Or the F voters could rank M alone in 1st place. That would work in IRV too
(nothing else would).

As I said, surely the purpose of a pairwise-count method is to _improve_ on
Bucklin.

>
> If you want a method that (like WV) meets Minimal Defense then I prefer
Forest's  "Max Covered Approval"  (which would nearly always be equivalent
> to Smith//Approval, which I also like.)

Smith//Approval shares the great vulnerability to truncation & burial.

Michael Ossipoff
>
> Chris  Benham
>
>
>
> On 10/7/2016 3:03 AM, Michael Ossipoff wrote:
>>
>>
>> Chris--
>>
>> Sure, the only reason to use MAM instead of MinMax is for if there's a
larger Smith set.
>>
>> We could propose MinMax, and assure people that the situations where it
fails MAM's criteria will never happen.
>>
>> I guess "Don't worry, it will never happen" is what FairVote assured
people in Burlington.
>>
>> Is that a good idea?
>>
>> And so, it's on the assumption that there could be a Smith set with more
than 3 candidates, that we speak of how MAM & Schulze differ.
>>
>> So, if it will be rare for them to differ, does that mean that we should
propose the more complicatedly-worded, elaborately- worded one?
>>
>> ...the less obviously, naturally and clearly motivated & justified one?
>>
>> MAM's brief definition just says:
>>
>> A defeat is affirmed if it isn't the weakest defeat in a cycle whose
other defeats are affirmed.
>>
>> Though CIVS never has a top cycle for 1st finisher, it often has them
farther down in the finishing order.
>>
>> I've only looked at the Smith-set of one of those: the poll regarding
laws for bigamy.
>>
>> It's Smith-set was approaching around 10 when I stopped counting. ( The
cycle was far down in the finishing order).
>>
>> Maybe short rankings caused that result, or maybe the 1-D spectrum
assumption doesn't hold for low finishing positions.
>>
>> Michael Ossipoff
>>
>>
>
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