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

Thu Nov 17 11:46:42 PST 2016

> Of the methods that combine Approval with pairwise-count, maybe PAV is the
> one that is most favorable to Approval, while still letting people vote
> rankings that count and letting pairwise-count have a role.
>
> Does that make it the best of that class?
>
> Michael Ossipoff
>
> On Thu, Nov 17, 2016 at 1:54 PM, 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.
>>
>> I now again consider Benham & Woodall to be the best proposals for an
>> electorate that wants &/or needs rankings...because of the IRV mitigations
>> that i mentioned in my previous posting, and because of the context of the
>> always high price of CD, as exemplified by MDDTR.
>>
>> It could be debatable whether IRV's CWs elimination problem is worse than
>> MDDTR's burial vulnerability problem, but, because of IRV's mitigations, I
>> tend to feel that IRV is better, _for people who want or need routine
>> ranking_.
>> Myself, I personally prefer MDDTR, with middle-ranking usually avoided,
>> but I'm talking about what's best for the electorate as a whole.
>>
>> In polls with balloting by both Approval & Score, I've observed
>> overcompromisers doing better with Score than with Approval. They (and
>> rival parties) would probably do even better with rankings.
>>
>> Suggested merit-order for electorates that want &/or need rankings:
>>
>> 1.Benham
>> 2. woodall
>> 3. IRV
>> 4. MDDTR
>> 5. Methods combining Approval with pairwise-count
>> 6. ER Bucklin/MJ
>> 7. Score
>> 8. Approval
>>
>> I still personally prefer Approval, or maybe MDDTR, when used as Approval
>> with 2nd-ranking as a defection-deterrent. But this suggested merit-order
>> is for electorates who want &/or need rankings.
>>
>> On pure merit, Woodall seems a bit better than Benham, because it's more
>> particular which Smith-set member it elects. But Benham is much briefer to
>> define, not needing to define or mention the Smith-set, and that makes a
>> big difference in proposability, which outweighs the small merit-difference.
>>
>> I don't know the merit-order among the methods that combine Approval with
>> pairwise-count.
>>
>> Maybe the ones that start with Approval are better than the ones that
>> start with pairwise-count.
>>
>> Among those, Brams' PAV is vulnerable to truncation, where MAMPO isn't.
>>
>> But maybe that's a good thing, if the majority CWs among the
>> majority-approved candidates isn't in your strong top-set.
>>
>> A proposal that the Greens upgrade from IRV to Benham seems reasonably
>> proposable.
>>
>> Though Benham & Woodall are vulnerable to burial & truncation, the worst
>> that can result from those strategies is the same as what IRV would have
>> done anyway.
>>
>> Michael Ossipoff
>>
>>
>>
>>
>>
>> On Thu, Nov 17, 2016 at 9:05 AM, C.Benham <cbenham at adam.com.au> wrote:
>>
>>> On 11/17/2016 9:00 AM, Forest Simmons wrote:
>>>
>>> Here's a simple method that is essentially Smith//Approval without
>>> having to mention the Smith set:
>>>
>>> List the candidates in order of approval, highest to lowest, top to
>>> bottom.  While any candidate pairwise beats an adjacent candidate higher in
>>> the list, switch places of the two lowest out of order adjacent members.
>>>
>>> When there remains no out of order adjacent pair, elect the candidate at
>>> the top of the list.
>>>
>>>
>>> Forest,
>>>
>>> I like Smith//Approval  and your usually equivalent Max Covered Approval
>>> method.
>>>
>>> But in this version, the stipulation that we  "switch places of the two
>>> *lowest* out of order adjacent members" could look a bit arbitrary and
>>> less smooth
>>> than Margins-Sorted Approval.
>>>
>>> BTW, it seems to me that both this and  Smith//Approval  can handle the
>>> Chicken Dilemma situation quite well if we use ranked ballots with
>>> approval cut-offs.
>>>
>>> (Or ratings ballots with many  slots that register approval and as many
>>> (or maybe as few as only 2) that register unapproval.)
>>>
>>> http://wiki.electorama.com/wiki/Approval_Sorted_Margins
>>>
>>> http://wiki.electorama.com/wiki/Approval_Cutoff
>>>
>>> And here's another smooth Condorcet method that should do as well:
>>>
>>> *Voters  score the candidates on some scale that allows large and varied
>>> gaps between the candidates: say 0-100.
>>> Elect the CW if there is one.
>>>
>>> Otherwise compress the 1-point gaps (if any) on all ballots into
>>> zero-point gaps (so that those ballots abandon their original pairwise
>>> preference for any
>>> X originally scored only one point more than any Y).
>>>
>>> Based on the thus modified ballot information, elect the CW if there is
>>> one.
>>>
>>> Otherwise compress the 2-point gaps (if any) on all ballots into
>>> zero-point gaps (so that those ballots abandon their original pairwise
>>> preference for any
>>> X originally scored two points more than any Y).
>>>
>>> Based on the thus modified ballot information, elect the CW if there is
>>> one.
>>>
>>> And so on, as gradually as possible compressing larger and larger gaps
>>> until we have a pairwise beats-all winner.*
>>>
>>> Chris Benham
>>>
>>>
>>>
>>> On 11/17/2016 9:00 AM, Forest Simmons wrote:
>>>
>>> Here's a simple method that is essentially Smith//Approval without
>>> having to mention the Smith set:
>>>
>>> List the candidates in order of approval, highest to lowest, top to
>>> bottom.  While any candidate pairwise beats an adjacent candidate higher in
>>> the list, switch places of the two lowest out of order adjacent members.
>>>
>>> When there remains no out of order adjacent pair, elect the candidate at
>>> the top of the list.
>>>
>>> Note that the winner will automatically be a member of the top cycle,
>>> and if it is a cycle of three, it will be the most approved member of the
>>> cycle.
>>>
>>> Also notice that it yields an unambiguous social order, and that there
>>> can be no second place complaint.
>>>
>>>
>>>
>>>
>>>
>>> On Tue, Nov 15, 2016 at 5:19 PM, Michael Ossipoff <
>>> email9648742 at gmail.com> wrote:
>>>
>>>> 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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>>>
>>>
>>>
>>
>
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