[EM] Challenge2 - give an example where MFBC is violated for Condorcet methods

[Peter Zbornik]

Kristofer,

thanks for sorting out the details.
I am not sure I buy your argument on LNHarm, as I do not how to
distinguish extremists from non-extremists within the framework of
election theory, where you only have the votes cast to take into
account, and these votes might or might not be sincere.

I'd say that the risks that LNH, FBC are violated, and that burial of
one specific candidate might lead to the victory of an other, all give
the incentive to bullet vote for the sincere favorite, which either
leads to noone winning the election, when respecting the empty vote,
or when the empty ballot is not respected, leads to the election
"nobodies", who might as well be "extremist" when the voting strategy
fails.

That's just my quite subjective view on the matter.

Best regards
Peter Zborník

On Tue, Jun 7, 2011 at 11:10 AM, Kristofer Munsterhjelm
<km_elmet at lavabit.com> wrote:
> Peter Zbornik wrote:
>>
>> Hi Kevin,
>>
>> I agree, FBC is a problem for all Condorcet elections and generalized
>> symmetric completion does not help.
>> I think something should be written about the FBC on Wikipedia (but
>> with an other name as someone (Jonathan Lundell?) proposed on this
>> list, in order to avoid "emotional" connotations with the word
>> "betrayal").
>> Thanks to the kind explanations and examples on this list I now get a
>> grip of the problem :o)
>> I am a bit slow starter (was like ten years since I studied maths.
>> I'd say that FBC (and LNH) is quite a big problem for Condorcet
>> methods, at least for someone (like me) who think sincere voting
>> should be the norm.
>> It seems that there is a risk, that Condorcet methods are reduced to
>> plurality-like methods due to voting strategies that exploit the fact
>> that FBC and LNH do not hold.
>
> I think burial is a more likely problem than FBC. As has been mentioned
> before, FBC is a problem when there is a cycle, but burial is a problem in
> certain cases where there's a Condorcet winner (depends on the magnitude and
> coordination of the strategy). Perhaps FBC is a greater problem than burial
> in the Condorcet-IRV hybrids, though.
>
> As for LNHarm, I'd say that breaking LNHarm is reasonable. If you vote "your
> side extremist > centrist > other side extremist", then it's reasonable that
> the centrist vote harms your extremist because he's better for society as a
> whole. Now, there's a chance that that would make true extremists simply
> truncate after "your side extremist", but then you lose nothing with respect
> to having a method that passes LNHarm.
>
>