[EM] MAM vs Schulze

[C.Benham]

Mike,

When it comes to Condorcet methods, I think that  (up to a point) some 
truncation incentive  (and so some "vulnerability to
truncation") is somewhere between a good thing and a relatively small 
necessary evil  ("necessary" to avoid greater evil).

> 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.
>

C: The methods I listed all meet Smith and Bucklin doesn't. Under 
Bucklin all voters have such a strong truncation incentive that
the method is more-or-less strategically equivalent to Approval.

Under Benham and  LV(erw) SME  informed strategists have a much weaker 
truncation incentive and in the zero-info. case there
is no truncation incentive.

Given that burial vulnerability is unavoidable in Condorcet methods, I 
think that is more democratic if  (in this respect) larger factions
have the advantage over smaller factions.

43: A
03: A>B
44: B>C  (sincere is B or B>A)
10: C

C>A  54-46,    A>B  46-44,   B>C 47-10.

Here A is the sincere CW and supported by the largest of the three 
factions of voters, but Winning Votes rewards the buriers by electing B.

Benham and  LV(erw)SME   easily elect  A.    Smith//Approval elects C.

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

C: Obviously the supporters of the sincere CW have much less truncation 
incentive under Smith//Approval than they do under Bucklin,
so  I wonder what example you have in mind.

40: A>B
35: B
25: C

The Condorcet winner is  A, but under Bucklin the A supporters' failure 
to truncate gives the win to B.

Chris Benham



On 10/9/2016 7:50 AM, Michael Ossipoff wrote:
>
>
> On Oct 8, 2016 6:06 AM, "C.Benham" <cbenham at adam.com.au 
> <mailto: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
> >
> >
> >
>

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