[EM] Trying to have CD, protect strong top-set, and protect middle candidates too

[Michael Ossipoff]

When I started my current EM participation, I was saying that 3-Slot ICT
was my favorite method.

That doesn't conflict with saying that I consider Approval the best,
because I regard 3-Slot ICT, or unlimited-rankings ICT (when used
approval-like) as an Approval version without chicken-dilemma.

Later I realized that MDDTR is better than ICT, because it gives better
protection to middle candidates.

I measure that protection by how well they'd be protected if they were
CWs.  ...what it would take to protect their win, and how well it's
protected.

I define "middle candidates" as candidates you rank or rate below top and
above bottom.

ICT gives no protection to middle candidates, against burial, or even
against innocent, non-strategic truncation--the two things that threaten a
CWs in pairwise-c0unt methods.

MDDTR gives full truncation-proofness to middle candidates, but (contrary
to what I earlier believed), its protection of middle candidates against
burial can only be called "shabby".

By the way, I no longer think that ICT or MDDTR needs to be 3-slot. 3-Slot
would be fine with me, because I believe that ICT or MDDTR should be used
as Approval, and that middle rating or ranking should only be used when
seriously needed to deter chicken-dilemma defection. When middle is used in
an unlimited-ranking MDDTR or ICT, it should probably consist of 2nd-place
ranking, if you want to give the demoted candidates the best protection.
...but maybe you'd rather rank them with respect to eachother, at different
middle levels, as I probably sometimes would.

But, as I've been saying, activists & organizations seem to like rankings,
and some people--overcompromisers & rival parties--might very well need
rankings to soften their voting errors.

And it seems to me that there's no particular reason not to rank, in order
of preference, your middle candidates, if some of them are better than
others, or if the voters of some of them are less trustworthy than others.

So, that's if you want CD, in addition to FBC, and good protection for
middle candidates

Even if you're using the method as Approval, you still want your demoted
candidate(s) to be well protected. Just because you don't trust hir voters
doesn't mean you want to throw her to the hounds and thereby lower Pt, the
probability of electing from your strong top-set.

Anyway, so far, this is all referring to CD methods.

Of those, I like MDDTR best. As a rank method, it (as i said) gives only
shabby burial-protection to a middle candidate. But evidently (please tell
me it isn't so) you can't have FBC, CD, and good protection of middle
candidates.

I consider CD more important to how well protected middle candidates are.
Yes, FBC + CD give poor protection to middle candidates, and that lessens
the value of their CD. But non-CD methods don't have CD at all, and that's
worse.

So I prefer MDDTR to methods that give better protection to middle
candidates, but don't have CD.

So, where I used to say that my favorite method is 3-Slot ICT, now I say
that my favorite method is MDDTR. Preferably with unlimited rankings.
(Though one could use only the 1st, 2nd, & bottom positions if one chose
to).   ...regardable as a chicken-dilemma-free version of Approval.

------------------------------------------------------------------

Non-CD methods with better "middle-strategy" than CD methods:

But, in an election, I'm just one voter, and so, how well-suited the method
is to me is less important, and won't affect the outcome as much, in
comparison to how well-suited the method is to lots of progressives.

So, what if most progressives would rather have a method that's really good
as a rank method, a method that has good "middle strategy" (strategy for
protecting a middle candidate's win if s/he's CWs).

That would be important if you knew that all or nearly all, or even most of
them were going to use the method purely as a rank method.

Bucklin is the traditional FBC rankings-method.

I distinguish 2 kinds of middle strategy merit:

1. How well the method protects top-ranked candidates against middle-ranked
candidates. I call that "Middle1"

2. How well the lmethod  protects a middle-ranked candidate against any
candidate you rank lower than hir. I call that "Middle2".

So, how to get the best middle strategy, with the main goal still being
keeping a good probability, Pt, of electing from your strong top-set?

MDDTR's middle1 seems better than that of Bucklin. In MDDTR, you're voting
to contribute to a majority for your top against your middle. In Bucklin,
you can protect top against middle by skipping some rating-levels above the
middle candidates. In that way, you can give the top candidates time to
receive the coalescing lower-choice votes that they'll get from the
preferrers of other candidates, before giving anything to the middle
candidates.

That's a bit more work than just ranking in order of preference. It
requires you to judge where, and how far down in rankings, your top
candidates are going to receive lower-choice votes from.

So I suggest that MDDTR does better at Middle1 than Bucklin does.

But Bucklin does better at Middle2.

In Bucklin, the CWs's win is protected by the people who pretty-much agree
with you, the people of your wing, merely not ranking down too far.

MDDTR needs that too, but it isn't enough to give MDDTR more than shabby
protection.

...And Bucklin's Middle1, though not as convenient or easy as that of
MDDTR, isn't as questionable as MDDTR's Middle2.

So, overall, I'd say that Bucklin's Middle Strategy is better than that of
MDDTR. So, for people who want to use the method purely as a rank-method,
Bucklin is better than MDDTR.

Bucklin also has the advantage of use-precedent.  MDDT has the advantage of
precinct-summability,but I don't consider that essential.

For voters using the method purely as a rank method, I'd prefer Bucklin to
MDDTR.

Chicken dilemma won't happen all the time, probably won't happen often. But
middle-protection will always matter to people using it as a rank method.

But it seems to me that, once we give up CD (for voters who need good
middle strategly, because of their rank voting), then it might be possible
to do better than Bucklin.

It seems to me that methods that use both Approval and pairwise-count can
do better than Bucklin, at middle protection.

A lot of methods of that kind have been proposed, and I've ignored all of
them because they don't meet CD. But, as mentioned above, for some
electorates, middle strategy could be more important.

It seems to me that MDDA (also evidently named MPOA) and Smith//Approval
are two methods that might be better than Bucklin at middle protection..

Using Approval as the cycle-solution is a very powerful idea (if you're
willing to give up CD, for an electorate's needs). But most of you already
knew that, before I paid attention to it (...because I was only looking at
CD methods)..

MDDA's & Smith//Approval's burial vulnerability doesn't matter much, when
the Approval winner wins the cycle. In fact, Smith//Approval's
truncation-vulnerability could even be regarded as an advantage, for when
your strong top-set doesn't include the CWs.

MDDA & Smith//Approval look better to me than Bucklin.

Simpler Middle1.

Precinct-Summability is an added bonus.

MDDA seems to have a briefer definition than either Bucklin or
Smith//Approval, and brief definition can be decisive.

I know of Bucklin being rejected when MDDTR was accepted. MDDA would almost
surely have been accepted too.

I don't  think Smith//Approval would go over well, with its need to define
the Smith set, which greatly lengthens the definition.

For an electorate that need good Middle1 & Middle2 more than CD, MDDA seems
the winner so far.

Smith//Approvsl of course meets Smith.  ...which of course means that it
fails FBC. But does it need FBC?

It could be argued (but I don't know if it's true) that Smith//Approval
doesn't need FBC, because, though you don't have an efffective Approval
vote at the top, you still can vote Approval, with the approval-cutoff, or
by only ranking your strong top-set.

So, though Compromise could become pair-beaten by Favorite because you
raise Favorite to top with Compromise, resulting in a cycle instead of a
CWv win for Favorite, the cycle will be judged by approvals, and you're
approved only your strong top-set.

Of course, just because Favorite was almost the CWv doesn't necessarily
mean that s/he'll win the Approval count. But are you any worse off than
you'd have been with MDDA?

Forest (but maybe others too) has proposed a number of methods that combine
pairwise-count and Approval. Do any of those beat MDDA & Smith//Approval by
the standards of protecting one's strong top-set, and Middle1 & Middle2?

in particular, do any of them do better than MDDA by those standards? Do
any do as well as MDDA by those standards and have as brief a defintion, or
nearly as brief a definition?

In other words, are there methods that achieve those things better than
MDDA & Smith//Approval, or achieve them better than MDDA and have as brief
a definition?

In fact, is there a method that meets FBC (or doesn't need it), meets CD,
and does as well by Middle1 & Middle2 as MDDA, Smith//Approval or Bucklin?

Michael Ossipoff
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