[EM] Kristofer: Mono-Add-Plump
nkklrp at hotmail.com
Thu Jan 5 14:08:24 PST 2012
> You haven't shown that Kevin's MMPO bad-example is a problem in that sense.
I think my primary objection is that it doesn't make sense.
Quite so. It doesn't make sense when compared to the Plurality results that we're
familiar with. MMPO differs drastically from Plurality, and can give results that
are disturbing if we expect Plurality-like results.
That's why the conditional methods might be the most feasible public proposals
for achieving FBC/ABE. They're solidly based on, and follow naturally from,
Approval and Plurality.
is aesthetic, perhaps it is based on logic.
...but it's regrettable if we have to forgo MMPO's _practical_ advantages because of that.
Yes, MMPO has a random-fill incentive and a burying incentive, but burial won't threaten
a set of candidates mutually AERLO-protected by a majority of the voters.
Of course practicality has to also include the matter of what's practical to propose
But, as I'll say below,
Plurality (the criterion) is much more than Plurality (the method)
Sure. I'm just saying that, because people are accustomed to Plurality and its results,
they don't like it when a method does something dramatically different from what Plurality
would do. But favoriteness isn't everything.
Of course the Plurality Criterion makes sense as an aesthetic desideratum. But we have to decide
what is most important.
But if Kevin's bad-example, and Mono-Add-Plump are a problem, I think some or most of the
conditional methods that comply with those criteria would be publicly acceptable. In fact,
they're the proposals that I'd start with, for that reason.
I think, though I am of course not certain of this, that the vast
majority of people would find something wrong with how MMPO resolves the
Probably. And the opposition to an MMPO enactment proposal would make sure everyone received
a copy of Kevin's MMPO bad-example, probably as a doorknob-hanger-brochure, and in the
Or to try to put what I think (and how I think people would react) into
more direct terms: this would be like "everybody but Bush" voters and
"everybody but Gore" voters (A and B plumpers respectively) wake up and
find that, because a single voter voted some obscure candidate (say
Hagelin) equal to Gore, and another voter voted the same obscure
candidate equal to Bush, that obscure candidate won.
Most likely, yes, they wouldn't like it, then, or when the opposition
publicized the possibility during the enactment campaign.
I'm interested in avoiding the worst strategy problems, but others are influenced by
other things, and there's a good chance that the public could be turned against MMPO
when Kevin's bad-example is publicized.
Sure, you could say that the everybody-but-Bush and everybody-but-Gore
voters should have clarified, in their ballots, that they do prefer Gore
and Bush (respectively) to Hagelin - but I think it would seem wrong to
the voters that they would have to do so, and that the method would not
just degrade gracefully if they did vote "everybody but Bush/Gore" right
Yes that's likely so.
The methods (MMPO & MDDTR) that avoid the ABE problem by counting pairwise
opposition have advantages, but could act in ways that could be unexpected
and seem outrageous to people familiar with the Plurality method's results.
The opposition in an enactment campaign would make sure that everyone heard
about those kind of possible results.
Sure, the noncompliances with the Plurality Criterion are more than just an
election of a Plurality nonwinner. And people's accustomed-ness to the Plurality
method can make them outraged when they see the similar, but bigger and more unexpected,
result when a method doesn't comply with the Plurality Criterion.
> Someone on this list was terribly bothered by the mutuality-requirement, referring to it as "sordid".
> He'll think this is terribly sordid, but if a faction of voters want coalition support for their
> candidate, why would it be important to them that they not support that coalition?
> They want to not help the people whose help they need?
> Oh what a cruel strategy-need to burden someone with! :-)
(I want to emphasize that most of the conditional methods, including most of the
ones based on mutual coalition, meet Mono-Add-Plump. When discussing conditional methods
that fail Mono-Add-Plump, we're only talking about MMT.)
When I read this, I recognized something that may explain others'
disagreement about the relative value of these criteria, and
mono-add-plump in particular.
In my mind, a preference ordering is (or should be) disconnected from
the method to which it is fed. In other words, a honest ranked ballot is
an expression of the wishes or preferences of the voter independent of
the voting system. In essence, he is saying "if it was up to me, I'd
have A, but if I couldn't have A, I would have B" and so on.
That's the (unattainable) ideal. Gibbard & Satterthwaite showed that it doesn't
work like that. One can just rank sincerely if one wants to, but one cannot
expect to optimize one's outcome thereby.
In that light, a criterion-based approach becomes much more sensible.
I've always liked criteria. FBC and Co-operation/Defection (CD) are criteria, for
an election method is a black box that takes preferences as inputs and
tries to "mechanically mediate" between the preferences to find the best
"Best social outcome" leaves a lot of room for disagreement. To me, the
method with the best social consequences is the one that best avoids
causing strategy problems that prevent an electorate from getting what they
most want. Favorite-burial and the co-operation/defection problem have particularly
detrimental social consequences.
, then it doesn't matter what happens inside the black
box. What matters is the relation between the outputs and the inputs. If
a method fails mono-add-plump, that means that when someone says "As for
me, I prefer A to everybody else", then the method uses that preference
to decide that "oh, A wasn't that good a choice after all". That may
happen because of mutuality requirements, or because of some unintuitive
internal logic, but the outcome changes in a way that is detrimental to
the voter who made the outcome change in the first place, and this voter
doesn't know anything about mutuality or coalition preferences or the
internals of the method when voting honestly.
In the examples that Chris posted, the plumping voters had no
strategic reason to do so. Plumping was obvious bad strategy in that
Yes it would be nice if everyone only needed to rank sincerely.
Maybe that ideal could be closely approached by AOCBucklin with AERLO, or
by MMPO with AERLO.
If others have this view of preference orderings as well, that could
explain why they don't like a method failing mono-add-plump, and why an
explanation of how the method works doesn't change their minds.
But how realistic is it to expect pure, naive sincere voting to always
Obviously, no method can pass every criterion, but mono-add-plump is
relatively "cheap" in that most methods out there pass it.
Most of the FBC/ABE methods that I like pass Mono-Add-Plump.
MDDTR and MMT are the notable exceptions. In the case of MMT, the folly
of the plumpers is easily shown.
Yes, MMT is suboptimal because, as you say, it doesn't avoid an avoidable
problem. MMPO, GMAT, AOC, MTAOC, MCAOC and AOCBucklin avoid it.
But what if MMT were the only proposable FBC/ABE method. As I said, I don't
think it is. I think that AOC, MTAOC and MCAOC are fully proposable.
It's necessary to do polling to find out which FBC/ABE methods are the
Only that will tell us whether people will reject MMT because of Mono-Add-Plump.
...if people will think that the coalition-rejecting plumpers are unfairly
treated in MMT.
And I repeat that the other conditional methods, other than MMT, don't fail
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