[EM] Generalizing "manipulability"

[Juho Laatu]

--- On Sun, 18/1/09, Jonathan Lundell <jlundell at pobox.com> wrote:

> 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?)

Yes, sorry about the confusion.

> 
> 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.

OK.

I think people are most often (e.g.
on this list) expected to have an
internal preference order of the
candidates, also when the ballots of
the method does not express it.

I also think that most often people
on this list assume that Approval
votes are expected to be strategic
while Range votes are expected to
be sincere (except that many assume
votes to be normalized, and that can
already be seen to be a strategy).

Juho