[EM] Generalizing "manipulability"

[Jonathan Lundell]

On Jan 17, 2009, at 10:38 PM, Juho Laatu wrote:

> --- On Sun, 18/1/09, Jonathan Lundell <jlundell at pobox.com> wrote:
>
>> On Jan 17, 2009, at 4:31 PM, Juho Laatu wrote:
>>
>>> The mail contained quite good
>>> definitions.
>>>
>>> I didn't however agree with the
>>> referenced part below. I think "sincere"
>>> and "zero-knowledge best strategic"
>>> ballot need not be the same. For example
>>> in Range(0,99) my sincere ballot could
>>> be A=50 B=51 but my best strategic vote
>>> would be A=0 B=99. Also other methods
>>> may have similarly small differences
>>> between "sincere" and "zero-knowledge
>>> best strategic" ballots.
>>
>> My argument is that the Range values (as well as the
>> Approval cutoff point) have meaning only within the method.
>> We know from your example how you rank A vs B, but the
>> actual values are uninterpreted except within the count.
>>
>> The term "sincere" is metaphorical at best, even
>> with linear ballots. What I'm arguing is that that
>> metaphor breaks down with non-linear methods, and the
>> appropriate generalization/abstraction of a sincere ballot
>> is a zero-knowledge ballot.
>
> I don't quite see why ranking based
> methods (Range, Approval) would not
> follow the same principles/definitions
> as rating based methods. The sincere
> message of the voter was above that she
> only slightly prefers B over A but the
> strategic vote indicated that she finds
> B to be maximally better than A (or
> that in order to make B win she better
> vote this way).


(I'd use rating/ranking opposite to that. No?)

I was making a smaller point, that the actual values in Range and the  
approval cutoff point in Approval are hard to interpret as "sincere"  
or not. On the other hand, we need a voter's "sincere" linear ordering  
of the candidates (ranking?) in order to be able to say whether an  
*outcome* is better or worse.