[EM] Sincere methods

[Juho Laatu]

On Apr 4, 2005, at 23:38, Kevin Venzke wrote:

> Maybe you have in an earlier post argued that majority rule (in this 
> sense)
> is not as necessary in a "sincere method." But I doubt I can be 
> convinced
> of that.

I'm not sure if I understood all you wrote, but anyway, if one 
sincerely thinks that majority rules should be respected, then 
corresponding sincere methods shall reflect that wish. Majority 
defending modifications should be excluded but sincere majority needs 
kept.

> What do you think of approval voting as a sincere method?

Definitely yes, approval is a very natural sincere measure that people 
may well see as a target for elections.

> WV is more likely
> to give an approval-ish result than margins is. I'm pretty sure 
> simulations
> could prove this easily.

May be, but the "ish" at approval-ish probably already means that we 
are not talking about our sincere target method but just about an 
approximation of it. I thus want people to say exactly what they want 
the election method to do and then name that method as the sincere 
method. Approval could be one, minmax (margins) could be one, sum of 
rankings could be one. Practical methods may then deviate from these as 
needed.

> Does it matter which measure is "more natural"? Does that affect 
> whether a
> method can be a "sincere" one?

Yes. I believe people think that that their sincere methods are 
natural, and on the other hand natural looking methods could be 
someone's sincere methods. Easy to understand strategy defence 
mechanisms can also be said to be natural (although they are not 
sincere). So, for all x, SincereMethod(x) => Natural(x)

>> The claim that WV methods would maybe not be sincere methods thus 
>> means
>> that to my knowledge nobody as so far claimed them to be _THE_ method
>> that provides the ideal result in a strategy free environment.
>
> To my knowledge, nobody makes such a strange claim about any method 
> except
> "average rating." But I suppose you define "ideal result" so that 
> Condorcet
> is satisfied.

If ranking based ballots are used, then Condorcet is most often 
required. I define sincere method so that it is relative to the used 
voting style. I.e. if votes are ratings, then the sincere voting method 
can be average rating, and if votes just indicate one candidate, then 
plurality could be the SVM.

> 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.

>> margins can be seen both as accurately
>> representing the ability to defend against changing candidate X to 
>> some
>> other candidate Y

> Is the "ability to defend against changing candidate X to some other
> candidate Y" really a consideration in a strategy-free setting?

Good question. I was afraid you would ask this :-). But yes, I think 
using this kind of arguments is ok since the actual election was seen 
as purely sincere. Word "defend" refers only to the situation after the 
elections. And also those "fights" after the elections are "straight 
forward attacks" and "free of strategical tactics".

>> Yes, most notably term "sincere criteria" excludes all criteria whose
>> target is to fight against strategies. Sincere criteria aim at 
>> electing
>> the best candidate and nothing more.
>
> I'm not sure this is well-defined. I can imagine interpreting 
> Condorcet,
> or the Majority criterion for solid coalitions, as anti-strategy 
> criteria.

If some criterion has both sincere and strategy defence based 
reasoning, then I'm happy to call it a sincere criterion.

P.S. I'm not familiar with "Majority criterion for solid coalitions"

>>> SVM: Schulze (wv), PVM: MinMax (pairwise opposition) and CDTT methods
>>
>> Schulze (wv) is to me a good PVM but I haven't considered it to be a
>> SVM (since I believe many of its features are related to fighting
>> against strategies, not to electing the ideal winner (with sincere
>> votes)).
>
> I still haven't understood what you mean by "ideal winner."

I haven't defined that term, sorry. I note that I have used "ideal 
winner" pretty much as a synonym for "winner of a SVM".

> I consider Schulze(wv) to be a good SVM.

But you include also some strategical concerns in the justifying text. 
=> In my mind when defining a SVM you should try to describe the ideal 
results without considering strategies. (I hope my definition of ideal 
winner clarified my use of term "ideal".)

> 49 A
> 24 B
> 27 C>B
>
> I say the most intuitive winner is B. It's true that I have some 
> strategy
> concerns in mind.

A seems to be the minmax (margins) winner (= my default favourite :-). 
Do you see B as a sincere winner too? For what reasons? Not being 
ranked at last place in majority of votes?

> I want to minimize voter regret, and get candidates an accurate number 
> of
> votes.

These sound more like sincere wishes about how a SVM should work.

> For a practical method, I suggest that C be elected with 53% 
> probability, and
> that B be elected with 47% probability. That's also due to strategic 
> concerns.

Ok. You refer to practical voting methods here. Using random selection 
could be possible is SVMs too, but that would mean that there is no 
"complete SVM" (= method that would be able to always pick the winner) 
behind but only a set of sincere criteria that leave some space for 
picking any of the "good enough" candidates as the winner.

> Unfortunately these MinMax methods aren't clone-independent. Surely the
> "ideal method for sincere voters" would be clone-independent?

I'm not quite sure if clone independence is a strategical defence 
criterion or a sincere criterion. Clones may also sometimes be real 
clones and sometimes not. Any good example in your mind for me to 
comment?

You caught me a bit unprepared in this. I'll try to study more to be 
able to give better answers later. I have some favourite techniques for 
handling clones but I'll come back when my thoughts are stable.

>> (Note that reason why I fear that sometimes strategy defence examples
>> could be misused is that one can claim that some method gives correct
>> result despite of certain strategic votes, but in this case the same
>> votes could be as well a result of sincere opinions, in which case 
>> they
>> should of course not be corrected.)
>
> If they're the result of sincere opinions, then there's no problem in
> "correcting" them.

I didn't get this. Did you say that sincere winner could be replaced 
with someone else? (="corrected")

Best Regards,
Juho