[EM] CD & truncation-resistance. Definitions people like.

Thu Oct 13 07:38:29 PDT 2016

Hi Chris--

(Replying farther down)

On Oct 11, 2016 10:55 PM, "C.Benham" <cbenham at adam.com.au> wrote:
>
> On 10/12/2016 12:12 PM, Michael Ossipoff wrote:
>
>> Regarding the CD example, Chris suggested scenarios in which one of the
other candidates, not A, is the CWs.
>
>
> 33: A>B
> 32: B (sincere may be B>A)
> 34: C
>
>
> Mike,
>
> I don't recall doing that exactly.   I like compliance with CD.   The
example I posted recently:
>
>> Given that burial vulnerability is unavoidable in Condorcet methods, I
think that is more democratic if  (in this respect) larger factions
>> have the advantage over smaller factions.
>>
>> 43: A
>> 03: A>B
>> 44: B>C  (sincere is B or B>A)
>> 10: C
>>
>> C>A  54-46,    A>B  46-44,   B>C 47-10.
>>
>> Here A is the sincere CW and supported by the largest of the three
factions of voters, but Winning Votes rewards the buriers by electing B.
>>
>> Benham and  LV(erw)SME   easily elect  A.    Smith//Approval elects C.
>
>
> The  "WV strategy" enthusiast might chastise the 3 A>B voters for
allowing the B supporters' burial to succeed by not truncating...

(endquote)

Yes. If you believe your favorite is CWs, you can protect hir win by
defensive plumping.  ...or at least not ranking someone whose voters might
bury.

You wrote:

but if they'd
> done that then WV would have elected their least-preferred candidate.

(endquote)

Yes, if the B voters bury, then for the A voters,  truncation will  only
worsen their result.

But such non-risk-free punitive defensive strategies are common throughout
the animal kingdom, including in human affairs.

1. Typically that CWs is a middle CWs, as in your example.

So the B voters in your example dislike C more than the A voters do.

A C victory will be worse for the B voters than for the A voters.

So the A voters have a more credible threat.

2. In such situations, the defender has a more credible threat.

The A voters could say to the B voters:

"Ok, let's get this straight: You're going to bury our candidate, and you
think we should show our gratitude by supporting your candidate in 2nd
place :^) ".

But, sure, there's at least the hypothetical possibility of the perpetual
burial fiasco, if A is in the B voters' bottom set.

But I've told why that fiasco's requirements are a bit mutually
contradictory.

Even if A is  in the B voters' bottom-set, the B voters might not bother
to  bury (even if it's theoretically optimal), if the chance of success is
sufficiently small.

I'm not saying that the majority are always right, but wv is popular.

Benham & Woodall don't reliability have wv strategy.

In Bucklin & Approval, the CWs's voters can protect hir by plumping.
Likewise methods with wv strategy.

Voters will do what it takes to protect a perceived CWs, because that's the
best they can get.

What happens when there's a CWs is more important than hkw a natural top
cycle is solved.

Michael Ossipoff

>
> The tops-of-the-ballots oriented Benham and  LV(erw)SME  handle the
scenario by (effectively) laughing off C (and electing A in breach of
> Minimal Defense), while the more bottoms-of-the-ballots oriented
Smith//Approval notes that C is the most "approved" (i.e. voted above
> bottom) candidate and says to the 44 B>C voters "since you voted for C
you can have C".
>
>
>> Chris recently mentioned an incompatibility between CD & Minimal Defense
(Eppley's votes-only version of SDSC or WDSC).
>
>
> C: Certainly we can't have all three of  Plurality, CD and Minimal
Defense.
>
>
>> When discussing Margins Sorted Approval, I objected that it penalizes
truncation instead of electing the CWs
>
>
> C: MSA isn't one of my very favourite Condorcet methods, but I prefer it
to Winning Votes.  In the example it elects C.
>
> Chris Benham
>
>
>> Regarding the CD example, Chris suggested scenarios in which one of the
other candidates, not A, is the CWs.
>>
>> What if B is CWs?
>>
>> Then we have a truncation example, in which the C voters are truncating
B.
>>
>> For C to win would be a violation of truncation resistance. ...if B is
CWs & this is a truncation example.
>>
>> But no problem: MMPO elects A instead of C.
>>
>> Chris recently mentioned an incompatibility between CD & Minimal Defense
(Eppley's votes-only version of SDSC or WDSC).
>>
>> Maybe the truncation resistance failure of electing C is related to that
incompatibility.
>>
>> Electing A avoids the problem.
>>
>> When discussing Margins Sorted Approval, I objected that it penalizes
truncation instead of electing the CWs. But that isn't really a problem:
>>
>> If your truncation is principled, then you have no reason to object when
the CWs thai you don't like doesn't win.
>>
>> ..nor does anyone have a complaint.
>>
>> If your truncation is careless, then just be more careful
>>
>> If your truncation is hurried, then allow yourself more time.
>>
>> So the election of A isn't a problem if B is CWs & it's a truncation
example.
>>
>> Plurality Criterion? Of the candidates other than the most
pairwise-opposed one, A is the most favorite.
>>
>> There's no important objection to electing A if B is CWs.
>>
>> What if C is the CWs, & the A voters are burying C?
>>
>> C would be a peculiar CWs, unsupported from both sides. No support other
than hir 1st choice voters.
>>
>> There's surely no important objection if such an unsupported candidate
doesn't win.
>>
>> So, no matter how you look at it, there's no objection to electing A in
the CD example.
>> --------------------
>> I told of how someone didn't accept ICT because of its relatively wordy
& unfamiliar definition.
>>
>> When offered list of methods, that person chose Approval as favorite.
>>
>> Hearing the MMPO definition, she didn't consider it un-intuitive,
complicated, overly wordy or without obvious justification.
>>
>> It elects someone least unpreferred to someone else.
>>
>> What could be more simple, obvious & natural?
>>
>> She didn't object to MMPO as she objected to ICS
>>
>> Yes there are strongly-felt objections to MMPO. I've answered them.
>>
>> Yes MMPO shares wv's possibility of perpetual burial fiasco, but it may
well never happen. It doesn't keep wv from being one of the most popular
methods.
>>
>> FBC, Weak CD, wv strategy. A lot of important advantages.
>>
>> Wv strategy means that the CWs is better & more easily protected than in
any other rank-methods.
>>
>> Michael Ossipoff
>>
>>
>>
>> ----
>> Election-Methods mailing list - see http://electorama.com/em for list
info
>
>
>
> ----
> Election-Methods mailing list - see http://electorama.com/em for list info
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.electorama.com/pipermail/election-methods-electorama.com/attachments/20161013/c27afca5/attachment-0001.htm>