[EM] FBC, center squeeze, and CD

[Michael Ossipoff]

On Sun, Nov 6, 2016 at 11:24 PM, C.Benham <cbenham at adam.com.au> wrote:

> On 11/7/2016 6:07 AM, Michael Ossipoff wrote:
>
> ...someone could say. "You didn't just favor X. You added a ballot,
> thereby spoiling a majority. It has nothing to do with the fact that you
> voted for X. You could have plumped for any of various candidates, and the
> effect would have been exacsly the same."
>
>
> "Someone" could *say* that, but it wouldn't make any sense.
>

But how so?


>
> But you can't say anything like that to to explain why X lost when I
> raised hir in my ranking. In that instance, making the ballot-set more
> favorable to X is the _only_ thing that I'm doing.
>
>
> Increasing the turnout is generally regarded as a good thing.  If the
> method used was one of the mono-raise failing methods I like (such as IRV
> and Benham), I would say:
>
> "Unfortunately it isn't possible for voting methods to have every
> desirable property (because some of those properties are mutually
> incompatible), and this method economises
> by not meeting mono-raise.
>

Exactly. The more properties, important desirable ones, a method provides,
the more of a cost there is, in terms of "embarrassment criteria",
"could-look-bad".

So it's a matter of what you're getting in terms of the "could-look-bad",
and whether that could-look-bad could be bad in a practical way. As you
suggested, MMPO's "Hitler-with-2-votes" would be bad news, and, as you
suggested, is more than a "look-bad".

But the Mono-Raise failure of Benham, Woodall & IRV is only a
could-look-bad. It never bothered me, and never stopped me from saying good
thins about those methods.

Likewise the lesser look-bad of MDDTR, when it fails Mono-Add-Plump.

MDDTR meets FBC & CD, and it has wv-like strategy.

...the same advantages that MMPO has.

...at the cost of Mono-Add-Plump.

You like IRV, Benham & Woodall. Lots of people here love IRV. I don't
reject those methods, though they aren't my main proposals, because of FBC,
and the fact that there's nothing the CWs's voters can do to protects hir
from losing, and the fact that Benham & Woodall are pairwise-count methods
very vulnerable to pairwise-count offensive strategy, and innocent,
nonstrategic truncation.

If you aren't majority-favored, the elimination of the CWs is disadvantages
for you. But, in Bucklin, sometimes it might not be known who the CWs is,
and s/he might not defenseiveliy plump, and so s/he (& you too) lose
anyway, even though it isn't IRV. I don't know that the Bucklin failure
that I just described will be rarer than the IRV failure that I just
described. And IRV brings some big advantages for people who are
majority-favored...MMC, CD, LNHa, LNHe.

If your candidate is big enough to eliminate the CW, then s/he's big enough
that s/he's fairly well-known, and that CW's voters would know something
about hir, and would be unlikely to reject hir & transfer the other way
when s/he's close enough to what you want that you'd prefer to elect hir.

So I don't reject IRV--I just don't emphasize it as a proposal.

Anyway, as I said, lots of people here love IRV, and its Mono-Raise failure
doesn't seem to hurt its popularity. You like IRV, and its Mono-Raise
failure doesn't put you off from it. I agree with you on that.

And, for the same reason, we needn't & shouldn't be put off by MDDTR's
Mono-Add-Plump failure.



>
> But generally speaking people care most about their favourites
>

True.


> , and IRV meets not only mono-add-plump but also mono-add-top. It's true
> that after the election
> some of losing candidate X's supporters could complain "If we hadn't
> top-ranked X, then X would have won" but that is unlikely to be noticed and
> of course isn't
> true of all (or anything like all) of X's supporters.  So the X supporters
> as a whole could complain "If we had been well informed and coordinated we
> could have
> used a mixed strategy (with not all of us voting the same way) and elected
> X."
>
> But if voters accept the method as fair and legitimate then that
> "complaint" won't be taken seriously or get much sympathy.
>

...as with MDDTR.


>
> Just as no quasi-intelligent device should be so "stupid" as to be
> confused by the very simple and spectacular MMPO failure example, neither
> should it be
> confused by the very very simple mono-add-plump scenario.
>

...or the fact that in IRV you can make someone lose by ranking them higher?


>
> What (arguably) desirable properties (or criterion compliances)  are
> incompatible with meeting Mono-add-Plump?
>

FBC, CD, & wv-like strategy are evidently require failing Mono-Add-Plump,
or having MMPO's Hitler-with-2-votes problem.

With MDDTR, the price of FBC, CD & wv-like strategy is Mono-Add-Plump.
That's a very small price, arguably less than IRV's Mono-Raise failure
(though I note that you mentioned that Mono-Add-Plump is about a favorite).

Michael Ossipoff

>
> Chris Benham
>
>
> Ok, thanks, Chris, for settling that matter. I guess we have to
> reluctantly give up Conditional Bucklin.
>
> But it would have been strategically great!
>
> Now, here's a question on a related topic:
>
> Say I arrive at the polling-place late. Before I arrive X is winning. I
> show up & plump for X, and that causes X to lose.
>
>
> ...is that worse than if I raise X in my ranking, and that causes X to
> lose?
>
> If so, why?
>
> It seems to me that the latter is worse than the former.
>
> I if show up late and plump for X, I'm doing two things: I'm adding a
> ballot, and I'm voting that ballot in a way that clearly should favor X.
>
> If i angrily complain, "Hey, how come, when I arrived and plumped for X,
> that made X lose??!"
>
> ...someone could say. "You didn't just favor X. You added a ballot,
> thereby spoiling a majority. It has nothing to do with the fact that you
> voted for X. You could have plumped for any of various candidates, and the
> effect would have been exacsly the same."
>
> But you can't say anything like that to to explain why X lost when I
> raised hir in my ranking. In that instance, making the ballot-set more
> favorable to X is the _only_ thing that I'm doing.
>
> So plainly violating Mono-Raise is worse than violating Mono-Add-Plump.
>
> Michael Ossipoff
>
>
>
> On Sun, Nov 6, 2016 at 10:27 AM, C.Benham <cbenham at adam.com.au> wrote:
>
>> The example I just posted of  "IBIFA with an anti-defection device"
>> failing FBC I'm afraid also works for both Mike's suggested
>> "Conditional Bucklin" and Forest's suggested "TopMiddleBottom".
>>
>> 20: F=C >>B
>> 07: F > C=B   (or, for the sake of Forest's method suggestion, F >> C=B)
>> 25: B
>> 48: W
>>
>> All three of these methods elect W, but if the 20 F=C >> B voters change
>> their rating of F from Top to Middle or Bottom
>> then the winner changes to B.
>>
>> Chris Benham
>>
>>
>>
>>
>
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