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

[Michael Ossipoff]

I don't mean that IRV isn't ok. IRV's Mono-Raise failure doesn't bother me.
Neither does MDDTR's Mono-Add-Plump failure.

Voting's purpose is probabilistic anyway. You vote to improve the
probability of a better outcome. The possible nonmonotonicity of IRV
& MDDTR doesn't invalidate that.

My point, in asking about when you make someone lose by raising hir from
last place to 1st place, was just that IRV is popular and widely used. It's
been used in Australia for a long time, and it's used in a fair number of
cities in this country.  ...and now has been adopted by the state of Maine.

...in spite of its Mono-Raise failure.

If the more embarrassing Mono-Raise failure doesn't give IRV any acceptance
or enactment problem, then why should the less embarrassing Mono-Add-Plump
failure of MDDTR give MDDTR an acceptance or enactment problem?

There of course have been objections to IRV, some valid, some not. But I
haven't heard any of the IRV critics in the various cities complain about
its nonmonotonicity. They object to implementation complexity. They
invalidly claim voting complexity. They invalidly complain because
supposedly voting is supposed to be by Plurality. They repealed IRV in
Burlington because of the elimination of a CWv.   But none of the
complaints that I've heard, in cities using it or considering IRV, have
been about its nonmonotonicity.

Why I say that Mono-Raise failure is more embarrassing:

With MDDTR, if your plump for X makes X lose, it's because you added a
ballot. It has nothing whatsoever to do with the fact that you voted
favorably to X.

With IRV, if raising X from bottom to top makes X lose, then X lost for no
other reason than because you helped hir more.

There are 2 kinds of nonmonotonicity:

Did you make X lose _in spite of_ voting favorably for hir?

or

Did you make X lose _because_ you voted hir more favorably?

Of those 2 kinds of nonmonotonicity the 2nd one is more of an embarrassment
to the method. There, the method is more directly acting oppositely to your
action.

Maybe it could be said that the 2nd kind of nonmonotonicity is twice as
embarrassing to the voting-system.

Anyway, if IRV is so widely used and successful, then why would
nonmonotonicity be a problem for MDDTR?

I now feel that IRV's (mitigated) problem isn't an unusually high price for
CD, isn't more than the "going rate" for CD. IRV & its derivatives are at
the top of my ranking of method-merit for electorates who want &/or need
ranking.

Michael Ossipoff







On Fri, Nov 18, 2016 at 1:23 AM, Michael Ossipoff <email9648742 at gmail.com>
wrote:

> 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/20161118/3535d2c2/attachment.htm>