[EM] Sincere methods

[Juho Laatu]

On Apr 13, 2005, at 18:44, Kevin Venzke wrote:

> I don't see a difference. What you call "majority defending 
> modifications"
> in e.g. winning votes is nothing more, nothing less than the use of a
> defeat strength measure that inherently views majority-strength defeats
> as being stronger than sub-majority-strength defeats.
>
> Suppose I think it's important to have peanut butter rather than jelly
> on my toast, so I decide that instead of using jelly, I will use peanut
> butter. Based on this discussion, I might expect you to claim that 
> peanut
> butter toast is a form of jelly toast, but with strategic modifications
> designed to defend people who prefer peanut butter.

Whatever you say is your true wish is a sincere opinion to me. It seems 
that peanut butter is your sincere target. Saying that you want jelly 
could be strategic if you think that the one who makes the toasts 
becomes jealous, reserves all the jelly for himself and leaves all the 
peanut butter for you.

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.

> 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.

> 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?

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.

>>> Do you have a favorite example in which, when all abstention in
>>> pairwise
>>> contests is informed and deliberate, margins produces a "more ideal"
>>> result
>>> than WV?
>>
>> I don't have any such favourite at hand. I guess I would favour 
>> margins
>> in any example where the results differ. Maybe you have some
>> interesting example in mind.
>
> 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.

> 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.)

>> 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.)

> 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.

> Maybe you think "SVM" is already well-defined, but you've suggested 
> that
> approval and margins could be used, and those aren't similar.

There can be many SVMs. This is because 1) people expressing their 
sincere opinions on SVMs are different, 2) the targets of the election 
may be different (sometimes we want to elect a compromise candidate, 
sometimes one that has many eager supporters etc.), 3) the available 
information may be different (rankings or ratings or just one candidate 
pointed out by each voter or maybe e.g. rankings+approval)

> 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.

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.

Justifying SVMs follows different logic than justifying PVMs. => 
Explanation why something is natural and wanted in theory vs. 
explanation why some method is most useful in real life (including also 
strategic considerations).

>>> 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. 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.)

> If you think "Minimize voter regret" is not a strategy concern, then I 
> note
> that in the above scenario, if A is elected, then the C>B voters will 
> regret
> that they ranked C, since surely if they had just voted "B," B would 
> have
> been elected.

Ok. This sounds like linked to strategies.

> If you really are not convinced that a sincere method should be 
> independent
> of clones, I won't argue with you, but that makes me doubt how "good" 
> the
> method is, even given sincere voters.

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'm saying that strategy defense mechanisms don't operate by detecting
> insincere votes.

I agree. That would be too difficult.