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

Thu Nov 17 22:23:13 PST 2016

Forest--

You wrote:

>
> But MAI still fails FBC.
>

Failing both FBC & CD isn't good.

>
> So to me the best proposal is ICA with default approval cutoff at
> truncation to help punish burial and truncation with an option to raise the
> cutoff to withstand a CD attack.
>

But buriers or truncators could raise that approval cutoff too. Someone
could bury X under Z without having to approve Z. That loses the deterrence
that would exist if that burier had to approve Z in order to rank hir over
someone, as would be so if ranking is counted as approval.

So CD still comes at the cost of a lot less protection against burial, or,
in ICT's case, trunction too.

But that just means that it isn't _better_ than MDDTR in that regard. It
doesn't mean that it's worse.

And it doesn't have Mono-Add-Plump failure.

So, the method has CD as MDDTR does, and trades truncation-proofness for
Mono-Add-Plump.

I value strategy protections more than embarrassment criteria. (But I
realize that proposal-opponents can use embarrassment criteria criticisms,
and that proponents aren't likely to be able to afford as much media time,
to answer the criticisms.)

[Replying farther down] :

>
> Here's my version (slightly different from the original):
>
> Candidate X strongly beats candidate Y iff
>
> the number of ballots on which X is ranked over Y is greater than
>
> the number of ballots on which Y is *ranked* equal to or greater than Y.
>
> [Note Y is not ranked equal to X if Y is not ranked.]
>
> If not all of the candidates are strongly beaten, disqualify all of the
> ones who are.
>
> Elect the most approved qualified candidate.
>
> I think that this method has all of the good properties of MDDA with
> mono-add-plump to boot.
>

I've only had a preliminary look at it, but it seems to me, right now, that
the separate approval-cutoff that the voter can raise from the default
spoils protection from burial & truncation.

You wrote:

> We still need to explore MDDA with the half power truncation rule, since
> it would also satisfy mono-add-plump if I am not mistaken.
>

Yes, it seems to me that a 1/2 power-truncation would get rid of the
Mono-Add-Plump failure. If, by not ranking a certain 2 candidates, you give
them each at least half of a vote against eachother, that would bring
Mono-Add-Plump compliance, it seems to me.

So maybe it would avoid criticism of MDDA.

But, if used with MDDTR, it would spoil CD.

You wrote:

> I agree with Chris Benham that mono-add-plump failure would be fatal in a
> public proposal.
>
>
What if you're going to rank X last in your ranking. With all the ballots,
including yours, X will win. But then you move X to 1st place in your
ranking, and that makes X lose.

Would that be ok?

Michael Ossipoff

> On Thu, Nov 17, 2016 at 2:12 PM, Michael Ossipoff <email9648742 at gmail.com>
> wrote:
>
>> I meant to ask: Did you say that MTRI doesn't pass FBC? How does FBC
>> failure happen? In return for FBC, it should beat MDDTR at vulnerability to
>> burial, and not be vulnerable to truncation.
>>
>> Anyway, anything you can tell me about the properties comparison between
>> MTRI & MDDTR would be helpful.
>>
>> MIchael Ossipoff
>>
>> On Thu, Nov 17, 2016 at 5:05 PM, Michael Ossipoff <email9648742 at gmail.com
>> > wrote:
>>
>>> For this method, MTRI, the procedural definition is more understandable
>>> than the recursive definition (though the recursive definition's brevity
>>> could be useful).
>>>
>>> So this is what I understand MTRI's procedural definition to be:
>>>
>>> 1. Order the candidates by their top-count score, with higher scores at
>>> top.
>>>
>>> 2. Switch the lowest pair of adjacent candidates whose lower candidate
>>> pair-beats the higher one.
>>>
>>> Repeat till there are no more pairs to switch. The highest candidate in
>>> the order at that time wins.
>>>
>>> -----------------------------------------------
>>>
>>> As a CD rank method, this method is a competitor of MDDTR. What are the
>>> property differences between MTRI & MDDTR?
>>>
>>> In particular, how does MTRI compare with MDDTR in regards to protection
>>> of a CWs against truncation & burial?
>>>
>>> Michael Ossipoff
>>>
>>>
>>> On Thu, Nov 17, 2016 at 2:55 PM, Forest Simmons <fsimmons at pcc.edu>
>>> wrote:
>>>
>>>> On Thu, Nov 17, 2016 at 10:54 AM, Michael Ossipoff <
>>>> email9648742 at gmail.com> wrote:
>>>>
>>>>> But wouldn't Smith//Approval, with approval cutoffs in the rankings,
>>>>> share MDDTR's burial-vullnerability?
>>>>>
>>>>> ...with, additionally, vulnerability to truncation, which MDDTR
>>>>> _doesn't_ have?
>>>>>
>>>>> And Smith//Approval trades MDDTR's FBC for Smith, which I consider an
>>>>> unfavorable trade.
>>>>>
>>>>
>>>> Perhaps make truncation the default approval cutoff, but let voters
>>>> move it higher as an option:
>>>>
>>>> 45 C
>>>> 30 A>B or A>>B
>>>> 25 B
>>>>
>>>> Voting A>>B would be the chicken defense (where sincere is 25 B>A).
>>>>
>>>> Voting A>B would be the truncation defense (where sincere is 45 C>B).
>>>>
>>>> With this option, MDDA would be an FBC compliant method that is
>>>> truncation and burial resistant as well as quasi CD compliant.
>>>>
>>>> Is there a way to modify MDDA to make it satisfy mono-add-plump?
>>>>
>>>> How about incorporating some form of power truncation.  When you plump
>>>> X and reduce the majority victory of Y over Z to a sub-majority, it would
>>>> revert to a majority if you counted the common truncation of Y and Z
>>>> against each other as even half a point.
>>>>
>>>> Btw, in case you didn't see it, one of my new favorite non-FBC methods
>>>> is Most Approved Immune(MAI):  Elect the most approved immune candidate.
>>>>
>>>> This means elect the most approved candidate X that is unbeaten
>>>> pairwise by the candidate that would win (recursively) if the method were
>>>> applied to the same ballot set with X disqualified or withdrawn.
>>>>
>>>> It is the simplest approval based rank method that confers immunity
>>>> from second place complaints on its winners.
>>>>
>>>> It is quasi CD compliant if voters can specify their approval cutoffs
>>>> above the truncation level when they want to.
>>>>
>>>> A top rank version of this method is fully CD compliant:
>>>>
>>>> Elect the Most Top Ranked Immune candidate. (MTRI)
>>>>
>>>> In other words elect the most top ranked candidate X that is unbeaten
>>>> pairwise by the candidate that would win (recursively) if the method were
>>>> applied to the same ballot set with X disqualified or withdrawn.
>>>>
>>>> Forest
>>>>
>>>>
>>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.electorama.com/pipermail/election-methods-electorama.com/attachments/20161118/3a6e7f0b/attachment-0001.htm>