[EM] Sincere methods

[Kevin Venzke]

Hi Juho,

 --- Juho Laatu <juho4880 at yahoo.co.uk> a écrit : 
> Should I read this so that for you some wv method is a sincere method. 
> That is ok to me and in line with the SVM definition. The fact that I 
> tend to see wv as a strategy defence mechanism should not influence 
> your sincere opinions. I.e. any method that someone claims to be 
> sincere and is able to convince himself of the "correctness" of the 
> method (and hopefully make also others understand the reasoning) is a 
> SVM to that person and probably a good SVM candidate for anyone.

Ok.

> > The example used below:
> > 49 A
> > 24 B
> > 27 C>B
> >
> > WV and Approval elect B, and this isn't a coincidence: both methods
> > consider the actual number of voters voting a certain way.
> 
> If approval is chosen as the SVM => B should win. If margins is chosen 
> as the SVM => A should win. If wv is chosen as the SVM => B should win.

Yes. But my point was that you don't seem to offer much guidance as to
what an "ideal" winner could or should be.

> > Well, I'm afraid I don't understand either how margins is "natural" or
> > how being "natural" suggests that something could be used as an SVM.
> 
> My justification for the naturalness of margins includes the following 
> explanation: "winner requires least additional votes to become a 
> Condorcet winner". Does this sound like a natural explanation to you 
> like it does to me?

Yes, it sounds natural when you phrase it that way.

> The latter part of your comment is more tricky. You use expression 
> "used as an SVM". I don't say that SVMs should always be used in 
> practical elections. That is possible but if e.g. strategy threats are 
> considered serious enough, one should use some other practical voting 
> methods (that probably are close to the SVM but offer better defence 
> against strategies) and leave the SVM only as a "theoretical 
> construction". But SVMs are natural by definition.

I'm not sure you answered my question. I didn't understand why naturalness
suggests suitability as an SVM. All you said relevant to this is that SVMs
are natural by definition. Do you mean that naturalness is all it takes to
be an SVM?

What if I invented a method, not natural or intuitive at all, involving
many calculations, which, when fed votes guaranteed to be sincere, produced
a superb winner 100% of the time? Could this be an SVM?

> > The 49 24 27 scenario is good enough.
> 
> Ok. If I try to defend margins as the sincere voting method, then my 
> explanation could be that A needs only 3 additional votes to become a 
> Condorcet winner. B needs 4 additional votes and is therefore slightly 
> worse than A. A can be said to be strongest in defending her policy 
> when in office because the difference between her supporters and 
> supporters of any other candidate is always positive or only slightly 
> negative. Although the supporters of A are neutral with respect to 
> battle between B and C and are likely to remain neutral also after B 
> would be elected, the C (with her supporters) would still cause more 
> serious opposition to B than anyone is able to cause to A.

>From this explanation it sounds like you think the only people who can
really revolt are those not matched by the opposition numbers; i.e., the
voters constituting the margin. In other words you suppose that when A
is elected, only 2 B>A voters can cause any trouble, since the other 49
can be restrained by corresponding A>B voters. I think that is a little
silly.

> > What I mean is that sincere criteria almost always have a strategic
> > justification.
> 
> The only thing that comes into my mind (on how sincere methods could be 
> linked to strategies) is that a sincere criterion can be said to defend 
> the correct winner. This could be called a strategy to defend the best 
> candidate, but I have used word strategy only in the sense of trying to 
> elect someone else than the best candidate that SVM would elect. I.e. 
> strategies in SVMs are designed to change the intended/wanted/ideal 
> outcome of an election. (Counter strategies could aim at electing the 
> correct sincere winner, but that is another story.)

So, what criterion is not a sincere criterion? Smith?

I say above that sincere criteria have a strategic justification, not 
because they "defend the correct winner," but because they relieve supporters
of the "correct winner" of having to vote in specific ways to get what
they want.

> >> P.S. I'm not familiar with "Majority criterion for solid coalitions"
> >
> > That is the one that says if more than half of the voters prefer every
> > candidate in some set of candidates to every other candidate, then the 
> > winner
> > must come from that set.
> 
> Ok, sounds like Smith set. Correct? (Or is the intention to say that 
> the _same_ group would prefer one candidate (or all candidates?) of the 
> set over all other candidates?) (And my answer to this part is the same 
> as the previous generic answer above.)

Smith implies it. Yes, it is the same group, preferring all candidates.

> > If that's what "ideal winner" means, then your statement above that you
> > "believe many of [Schulze(wv)'s] features are related to fighting 
> > against
> > strategies, not to electing the ideal winner" doesn't make any sense,
> > since my claim is that Schulze(wv) is a good SVM.
> 
> I note again that I accept that some people find different methods 
> sincere than others.
> 
> For me finding a natural (SVM) explanation for Schulze(wv) has not been 
> easy. I start my search from thinking what the winning paths might mean 
> in real life, and I have failed to find a good explanation. There is 
> nome naturalness in the paths but not enough that I would be able to 
> convince myself that it is just the Schulze(wv) winner that is the 
> obvious best candidate.

Ok, I think I understand. You really want a method that is simple to explain.
I think perhaps one could actually start with MinMax(pairwise opposition),
which is very easy to explain: Elect the candidate who minimizes the maximum
number of votes against him in some contest.

Very simple, but it has problems: It fails Condorcet, Smith, Majority,
Plurality, and Clone-Winner.

So perhaps we "upgrade" to MinMax(wv), so that Condorcet and Plurality are
satisfied. The definition change is that instead of "...against him in some
contest," it's "...against him in a *losing* contest."

But we still fail Smith, Majority, and Clone-Winner. We could use Schulze(wv)
to fix those. The use of beatpaths allows clones' wins over each other to be
canceled out, in a sense.

> > The more I talk with you, the more I am convinced that there is no way 
> > to
> > justify a method except in strategic terms. The only justifications 
> > you have
> > used so far are "naturalness" and a kind of "immunity to mutiny" 
> > (which I
> > don't think counts).
> 
> "Naturalness" is to me an essential part of SVM. "Immunity to mutiny" I 
> used only to give rationale why margins could be claimed to be a SVM.

Hmm, I still don't understand this. I can understand if "naturalness" is a
prerequisite to being an SVM. But what does "immunity to munity" have to do
with it?

> I think I lost you here since the difference between sincere methods 
> and strategies is so clear to me that I find it hard to see why all 
> methods would be linked to strategic considerations. Maybe your 
> definition of strategy is different than mine. As explained above, I 
> see strategies pretty much as attempts to deviate from the 
> ideal/sincere voting results.

Well, if by "naturalness" you mean "intuitiveness" or "ease of understanding," 
then I can see that a method could be justified using those reasons.

> >>> 49 A
> >>> 24 B
> >>> 27 C>B
> 
> > I see B as a sincere winner. A can't win because this would be contrary
> > to majority rule (in any way I've defined it). C can't win because by 
> > any
> > measure, C seems to have done worse than A.
> >
> > You haven't offered an SVM choice that would preserve majority rule, 
> > in my
> > sense.
> 
> True. I guess we are talking about the Smith set. 

No, since all three of those candidates are in the Smith set. I'm talking
about the principle which says (among other things) that if there is only
one majority-strength decision, such as B>A, then you can't elect A.

> To me electing 
> someone outside the Smith set is ok in some extreme cases. This is a 
> violation against majority opinion in the sense that majority prefers 
> someone to this candidate. But electing someone from the Smith set 
> violates also the same majority rule. (To me Smith set does not 
> represent any new additional strong majority rule but is just a 
> collection of smaller majority preferences in the spirit described 
> above.)
> 
> I understand that many people see Smith set as a natural sincere 
> criterion. And as a result Smith set based methods are SVMs to many. (I 
> have criticized use of Smith set in some other mails because of its 
> links to trying to linearize group opinions.)

Ok. My view is that Smith is important for clone reasons. It seems like
a problem that in MinMax methods, votes for similar candidates, by the same
voters, can cause all of those candidates to lose, and cause a candidate to
win who pairwise didn't win any contests.

> I agree that independence of clones is a nice idea but I'm not familiar 
> enough and not convinced enough of the available definitions (if they 
> always refer to true clones) and need to respect these criteria over 
> other voter preferences to give my final opinion on what criteria are 
> sincere to me. Hoping to come back as I said. Smith set sounded natural 
> to me first but after some thinking I now find it just a criterion that 
> should apply in 99% of the elections. I'm not sure about the clones 
> yet.

I don't know what you mean by "true clones." A method that chokes on "fake
clones" will also choke on "true clones" since it can't tell the difference.

I hear you saying that you don't know whether clone independence is a
"natural" concept. Am I right? Because whether clone independence is a natural 
concept or "sincere criterion" is a matter of opinion, and of no practical 
importance. It's not interesting to have a discussion with you about Smith or 
clone independence if you're not talking about practical methods that could 
actually be used.

The thing that would change this, is if you want to argue that sometimes
Smith or clone independence causes a worse candidate to be elected. But I
don't think that's what you're saying.

Kevin Venzke



	

	
		
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