[EM] Meta-criteria 6 of 9: Heuristics. #1, simplicity

[Kevin Venzke]

Hi Juho,

--- En date de : Sam 8.5.10, Juho <juho4880 at yahoo.co.uk> a écrit :
> > Hi Juho,
> > 
> > --- En date de : Ven 7.5.10, Juho <juho4880 at yahoo.co.uk>
> a écrit :
> >>> *Who* must have considered winning votes to
> not be
> >> optimal with sincere
> >>> votes?
> >> 
> >> I don't really know what others have thought. My
> first
> >> approach when I first time thought about pairwise
> comparison
> >> based methods was that margins would be a natural
> and simple
> >> way to measure preference strengths, and I needed
> an
> >> explanation to why one would use wining votes.
> The
> >> argumentation that I found was related to
> strategic voting.
> >> 
> >>> Never mind that you noticed above that WV
> advocates
> >> tend to have a
> >>> different conception of truncation. (Though I
> wouldn't
> >> call it
> >>> disapproval; disapproval is likely, but the
> point is
> >> abstention.)
> >>> 
> >>> The arguments I remember are about majorities
> and
> >> sincere CWs more than
> >>> about fixing strategic incentives for its own
> sake.
> >> 
> >> There have been arguments that the reason why
> margins is
> >> not good is its strategic vulnerabilities when
> compared to
> >> winning votes. (This means that winning votes have
> been
> >> considered to be better because of strategy
> related reasons.
> >> But this doesn't say anything on if someone finds
> winning
> >> votes to be ideal with sincere votes.)
> > 
> > And it doesn't say anything on whether someone finds
> margins to be ideal
> > with sincere votes.
> 
> It's just me and some others that have said that margins
> seems at least more natural than winning votes (not
> necessarily ideal).

Ok, good. I just want to be clear on who is saying this.

> > What *does* mean that WV is considered to be better
> with sincere votes
> > is the perspective that when voters truncate they mean
> to abstain, and
> > not lend weight to the ignored contests.
> 
> What does "abstain" mean? Margins thinks that 40-30 and
> 30-20 opinions are of same strength. Should we consider the
> strengths of those opinions to be (40-30)/70 and (30-20)/50?
> Now we treat the truncated and equal rankings in some sense
> as abstentions. This approach has also been discussed but it
> is not winning votes. With this approach opinion 30-20 is
> stronger than 40-30 (unlike in winning votes). It differs
> from margins in that it counts how much stronger the winning
> side is in percentage (not in number of votes as in
> margins).

I don't remember this approach being discussed but it's not how I would
do it. You wouldn't start with the margin: margin is a hybrid between
the ratio and the absolute vote count. What you would do is say that
40:30 is 40+30 = 70, and 30:20 = 50. That, perhaps, is what WV wants to
be.

On the other hand, maybe WV just wants to respect majorities expressed
over majorities that can only be calculated to exist due to vote 
splitting. The "abstain" could mean "don't count my vote when looking for
majorities."

"Abstain" could mean "detract from the importance of the contest."
This is important when the race is over when voters decide whether the
method respected the most important contests.

> I don't have any better explanations to winning votes as
> the ideal way to measure preference strengths (better than
> "number of votes on the winning side against some other
> candidate").

Suggest another rule that respects majorities.

> >>> FPP has strategic problems beyond those found
> in
> >> IRV... We don't conclude
> >>> from this that FPP is better with sincere
> votes. We
> >> don't take arguments
> >>> about FPP's strategic problems as an admission
> that
> >> "otherwise" (???) FPP
> >>> was just fine.
> >>> 
> >>> Why couldn't I say that the point of *margins*
> is to
> >> minimize a strategic
> >>> incentive?
> >> 
> >> There are cases where margins are less vulnerable
> to
> >> strategic voting than winning votes but I don't
> recall
> >> anyone saying that margins would have been
> designed with
> >> this in mind.
> > 
> > I'm talking about truncation here, and the way margins
> makes it useless.
> 
> I think the margins philosophy is that truncations and
> equal rankings are both treated as equal rankings. Or do you
> mean that truncation should be interpreted as some kind of
> "implicit approval cutoff"? Should "A=B>C" be treated
> differently than "C>A=B" or "C" with respect to the
> pairwise comparison between A and B? Or do you refer to
> truncation as a strategic defence mechanism?

I'm talking about the fact that in margins, truncation and equal ranking
are useless, things you could never calculate that you should do (in a
public election). This can be claimed as a strategic advantage of margins
and a strategic weakness of WV.

> > My point is more that I don't know of any coherent
> explanation of why
> > margins is "ideal" with sincere votes, and WV is not.
> But that explanation
> > must be out there if the only problem WV advocates
> have with margins is
> > its strategic incentives. There must be some
> 10+-year-old posts from WV
> > advocates unhappy that they can't just use margins.
> 
> There are many mails and web articles. But maybe less on
> the performance with sincere votes than about strategies. At
> least according to my experience it is difficult to raise
> good quality discussion on that very central topic.

I would say that's because it's difficult to understand what it refers to.
Sometimes people write criteria to say how a method should behave,
without direct reference to strategy, such as Condorcet, Plurality,
Smith, or CDTT. I don't know what the margins standard is other than
that its resolution rule can be explained in few words. Even the notion
that an equal ranking should be treated as a split, self-opposing vote
seems to be based in strategic concerns.

> > I guess what you mean to point out is that WV actually
> does ignore a
> > type of preference actually expressed. Fair enough,
> but it doesn't matter
> > to my point, which is just that WV actually does have
> logic that has
> > a resemblance to - and is as completely arbitrary on a
> purely aesthetic
> > level as - the principle of adding/removing as few
> ballots as necessary
> > to create a CW.
> 
> I wonder if someone has somewhere written a description on
> how winning votes is intended to measure sincere opinions.

You already did. You observed that WV advocates tend to see a different
meaning to truncation. This is a different concept of sincerity that WV
accomodates.

When I run simulations and I see a bullet vote "A" to me this does not
mean "A>B=C" due to the fact that in a public election that interpretation
would be presumptuous and unrealistic.

If the setting were different, where voters are supposed to be 
knowledgeable about all the candidates and vote the whole ranking whether
they want to or not, and it could be expected that the voters would
never be torn on whether to use strategy or risk giving the election
away (I say "strategy": in the form of burial this could have a defensive
or offensive intent in margins, and that's why I think it's a big problem
to remove truncation as an option) then I might have a use for the 
margins standard of sincerity.

> P.S. My biggest fears with winning votes is that it might
> in some real elections (with sincere votes) produce a result
> that people do not find natural.
> 
> 10: A>B=C
> 20: A>B>C
> 16: A>C>B
> 01: B>A=C
> 01: B>A>C
> 26: B>C>A
> 03: C>A=B
> 03: C>A>B
> 20: C>B>A
> 
> This set of votes is cyclic. B and C are from the same wing
> (they support each others). But should C win (as in most
> methods with winning votes) although B has more first
> preferences than C and also A supporters like B more than
> C?

As long as A loses I don't care that much. If voters care so much about
a 2% difference in FPs then we are generally in trouble. (What principle
does margins adhere to that prevents this from being a problem in
general?) And not even half of the A voters supported B.

The public needs to ask themselves what A>B=C means. They should have a
look at those ballots. (Really I would say it's only fair for truncation
to be completely banned in margins, except that I think that people 
truncating without meaning to say "all the worst candidates are exactly
equal" would actually be causing less damage than if we forced them to 
come up with something.)

Kevin Venzke