[EM] majoritarian top ratings (MTR) (sent to EM list Dec.12)

Kevin Venzke stepjak at yahoo.fr
Sun Jan 21 15:12:07 PST 2007

Late reply:

--- Chris Benham <cbenhamau at yahoo.com.au> a écrit :
> Kevin Venzke wrote:
> > My favorite method lately I'll call "majoritarian 
> > top ratings" or "MTR."
> > I don't believe it has been suggested on the list. 
> > 
> > Here is the definition:
> > 1. The voter gives every candidate the "top" rating,
> > the "middle" rating,
> > or no rating at all, which is the bottom rating.
> >
> > 2. Say that a candidate X is "defeated by a
> >majority" if more than half
> > of all voters assign some other candidate Y a
> >strictly higher ranking
> > than they assign to X.
> >
> > 3. Elect the top candidate in the ordering of
> >candidates wherein a candidate X is above candidate Y
> >when X is not defeated by a majority
> > while Y is, or (when this makes no distinction) when
> >X received the top
> > rating on more ballots than did Y.
> >
> Kevin,
> Is there some reason apart from simplicity that you
> use MDD instead of  CDTT?

Yes. CDTT won't satisfy FBC generally.

> > Advantages of this:
> > 1. FBC
> > 2. (my interpretation of) minimal defense
> > 3. limited later-no-harm, in that you can't hurt
> >your top-rated candidates
> > by listing middle-rated candidates.
> >
> I suppose you can add the "3-slot versions" of 
> Smith(Gross) and  Majority for Solid Coalitions.

That sounds right...

> > Disadvantages:
> > 1. fails Plurality (although not as egregiously as
> >MMPO)
> > 2. potential for burial strategy (although with the
> >usual countermeasures)
> Take the 0-info. voters whose main or only preference
> is between candidates they regard as acceptable and
> all the others they regard as unacceptable
> (i.e. they have one big gap in their sincere ratings).
> For them the sincere way of voting would be to ignore
> the middle slot and just submit an approval vote,
> putting all the unacceptables in the bottom slot.
> But in fact their best strategy is to randomly select
> half the unacceptables and put them in the middle
> slot, maybe causing one that would otherwise beat
> an acceptable candidate to be disqualified.

That's true. I think that's inevitable when there's a LNHarm guarantee
but no LNHelp guarantee.

> With information, the middle slot would mainly become
> a cynical strategy-tool for factions to try to
> disqualify the most electible candidate/s in rival
> faction/s. The effect of that could be the election of
> a "turkey" with little sincere support.

And that possibility is the incentive to not do that. I don't see that
this is much different from other methods that have burial potential.

> It seems to me that FBC/SF compliance is just so
> "expensive" and to me uninspiring and "negative
> minded". My favourite 3-slot method definitely remains
> "3-slot DMC".
> FBC complying methods generally at least verge on
> being strategically equivalent to plain Approval (in
> the case of MTR, with extra burial opportunities and a
> random-fill incentive).

Well, with say 3-slot ICA, you have two slots representing approval.
The pairwise component creates a significant distinction between these
two slots, but if it comes down to approval, the two slots count as
the same thing.

With MTR only the top slot represents approval. The second slot is more
like a mechanism to indicate which candidates (i.e. the unvoted ones) are
the worst.

My concern is that Approval can pick a bad winner even when there are
just three candidates. So I wanted to add some ability to be more
expressive, without ruining Approval's advantages.

Possibly I could come up with a compromise method that wouldn't be so
vulnerable to burial.

Kevin Venzke


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