[EM] Schulze definition (was: information content, game theory, cooperation)

[Árpád Magosányi]

2009/6/7 Raph Frank <raphfrk at gmail.com>

> On Sun, Jun 7, 2009 at 7:35 PM, Árpád Magosányi <magwas at rabic.org> wrote:
>
>> """"
>> - The electors rank the candidates according to their preferences.
>> - If there is a group of candidates all preferred over all candidates
>> outside the group, then ignoring the candidates outside the group should not
>> change the outcome of the election.
>> - The winner should be choosen from the above group in a way that
>> guarantees that if a candidate similar to an already running candidate is
>> introduced, the outcome of the election is not changed, and the less
>> controversial candidates are preferred.
>> """
>>
>
>
> Ok, so you are basically saying (in simple terms)
>
> A) the method is a ranked method
> B) All candidates outside the Smith set can be ignored without changing the
> result
> C) The method should be clone independent.
>

Not exactly.
C/1) The method should be clone independent
C/2) The method should prefer weak defeats

Actually C/2 is the one where I yet to became confident that there is a
one-to-one match between the wording and the exact mathematical definition.

 [...]

>
> Schulze and ranked pairs are the only methods that meet clone independence
> and the condorcet rule.
>
> Does ranked pairs fail the Smith criterion?
>

No. It fails the prefer-weak-defeats criterion only from the above.

>
>
> I would change B to "If there is a group of candidates all preferred over
> all candidates outside the group, then only those candidates may win and the
> candidates outside the group may have no effect on the result".
>
> If you don't restrict the winner to the Smith set (which your rules don't
> necessarily), then you could end up with a non-condorcet method.
>

B does restrict the winner to the Smith set. If someone outside the Smith
set wins, ignoring him would change the election result.


>
>
> Also, just because the popular/proposed condorcet methods are excluded by
> your definition doesn't mean that some other weird method can't be found
> that also meets the rule.
>

This is why I have put clone independence back.

>
>
> It might be better to just include the reasons that you like Sculze and use
> those rules rather than trying to select Sculze by a process of elimination.
>

Actually I end up doing so. I did not include monotonicity because I don't
view it as very important, but include cloneproofness because I do. (I am
hoping that a nonmonotonic method matching all other criteria should not be
very bad in most cases.)
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.electorama.com/pipermail/election-methods-electorama.com/attachments/20090608/6bb42453/attachment-0004.htm>