[EM] FBC, center squeeze, and CD

[Michael Ossipoff]

Correction of an unintended word:

When I said:

"In the 1st round, if a ballot gives conditional 1st ranking to a candidate,
that 1st ranking is given only if..."

Instead of "...that 1st ranking is given..."

I meant:

"...a vote is given..."

Michael Ossipoff



On Sat, Nov 5, 2016 at 3:41 PM, Michael Ossipoff <email9648742 at gmail.com>
wrote:

> Because it's so brief, let me state the conditional(u) option, for
> Approval, and for Bucklin:
>
> Approval:
>
> If a ballot conditionally approves a candidate, then it gives an approval
> to that candidate only if that vote-receiving candidate has more
> unconditional approvals than does any candidate unconditionally approved by
> that ballot.
>
> Bucklin:
>
> 1. At 1st rank:
>
> In the 1st round, if a ballot gives conditional 1st ranking to a
> candidate, that 1st ranking is given only if that vote-receiving candidate
> is unconditionally 1st-ranked on more ballots than is any candidate
> unconditionally 1st ranked on that ballot.
>
> 2. At any rank other than 1st:
>
> In a round, at some non-1st rank, if a ballot gives a conditional vote to
> a candidate, then that ballot gives that candidate a vote in that round
> only if that vote-receiving candidate has a higher vote-total (as of just
> before that round) than any candidate unconditionally 1st-ranked on that
> ballot.
>
> Michael Ossipoff
>
>
>
> On Sat, Nov 5, 2016 at 3:28 PM, Michael Ossipoff <email9648742 at gmail.com>
> wrote:
>
>> Hi Jameson--
>>
>> The choice among the 3 goals you name is a subjective choice, with no
>> wrong choice of goal.
>>
>> So we can amicably prefer differfent goal-choices & different solutions
>> to achieve them.
>>
>> To me, FBC is essential.
>>
>>  ...because...
>>
>> 1.  Many people won't consider not fully helping some compromise (maybe a
>> really odious "compromise" like Hillary).  At least let them also fully
>> support their favorite, and other better candidates when doing so.
>>
>> 2. Because of the importance of the strong top-set, and maybe the
>> ordinary top-set too, it's important to always allow the option of
>> fkully-effective strategically optimal approval-votilng, equal top rating
>> or ranking.
>>
>> #1 applies mostly just to current conditions. #2 applies in any
>> conditions.
>>
>> As you said, reliably electing the CWs (& in rank-methods, the CWv) is
>> incompatible with FBC. Therefore I reject the Condorcet Crirerion (CC) as a
>> goal. As you or Chris mentioned, the center-squeeze concern is closely
>> related to CC.
>>
>> It's possible to get CD & FBC. Therefore, a genuinely _best_ method
>> should have both.
>>
>> Because MMPO must reluctantly be abandoned (Chris finally convinced me)
>> because of its "Hitler with 2 votes" problem, then:
>>
>> The best methods are Conditional Approval & Conditional(u) Bucklin.
>>
>> ...But I repeat that the choice among your 3 goals is subjective and
>> individual, and that there's no wrong choice. I'm just stating my own
>> choice.
>>
>> Of course, for a first proposal, for a first reform from Plurality, brief
>> definition is essential. Also, the easiest possible implementation, without
>> any new balloting-equipment or software, might be advantageous, making
>> Approval the best first proposal.
>>
>> But, if people want rankings (and many do, and many likely need them, to
>> soften their voting-errors), then Bucklin has the advantage of relative
>> brevity, and use-precedence.
>>
>> Or, if new balloting & software is feasible (as would be necessary for
>> Bucklin, then Conditional Approval could be considered.
>>
>> Conditional(u) Bucklin, adding some to the definition-length of Bucklin,
>> might or might not be publicly acceptable, by the public's brevity-standard.
>>
>> Michael Ossipoff
>>
>>
>>
>>
>>
>> On Sat, Nov 5, 2016 at 2:32 PM, Jameson Quinn <jameson.quinn at gmail.com>
>> wrote:
>>
>>> We've had some productive discussions recently about methods that
>>> attempt to deal with FBC, center squeeze, and chicken dilemma. (Note that
>>> "deal with chicken dilemma" could mean one of two things: punish betrayal,
>>> or avoid a slippery slope. There are differing opinions as to which of
>>> these is better.)
>>>
>>> But there is a fundamental tension between these three characteristics.
>>> After all, center squeeze is really just a special case of the Condorcet
>>> criterion; and FBC and Condorcet are well-known to be incompatible.
>>>
>>> Why are those two things incompatible? Because in a Condorcet cycle,
>>> with a Condorcet-compliant voting system, if the other two groups vote
>>> honestly, then your faction can guarantee electing your second choice by
>>> betraying your favorite. So if you expect your least-favorite to win,
>>> betrayal is strategically forced.
>>>
>>> Essentially, in a cycle of 3, sticking with your favorite is a signal
>>> for the group who likes your second favorite and hates your favorite that
>>> your favorite is a threat, and they'd better compromise because you're
>>> unwilling to.
>>>
>>> My various recent proposals have tried to thread this needle in
>>> different ways:
>>>
>>> MAS gets FBC, no-slippery-slope CD, and (with some explicit strategy)
>>> center squeeze, by having two middle ranks: an upper level to signal
>>> willingness to compromise even with a smaller faction (as in center
>>> squeeze), and a lower level to signal the idea that you expect the larger
>>> faction to be correct (as in chicken dilemma).
>>>
>>> PAR gets no-slippery-slope CD, strategy-free center squeeze, and comes
>>> close to (but fails to reach) FBC, by automating the strategic choice for
>>> middle votes. Unfortunately, that makes it too close to
>>> Condorcet-compliant, so that FBC breaks.
>>>
>>> PAR-prime is basically the same compromise as PAR, but slightly extends
>>> the cases where center squeeze works, at the cost of a bit more complexity
>>> of description.
>>>
>>> QQQ gets FBC, no-slippery-slope CD, and handles the more clear-cut cases
>>> of center squeeze, at the cost of EXTREME complexity of description, by
>>> barely sipping the strategic information from other votes, so that the
>>> drops of strategic information that your vote leaks to opposing factions
>>> can be equalled by an ideal FBC-compliant ballot.
>>>
>>> Other proposals (ICT, IBIFA, conditional approval, etc.) have other
>>> interesting attempts to resolve this trilemma.
>>>
>>> Essentially, if you have a method that deals with center squeeze and
>>> no-slippery-slope CD, then there are two possibilities. Either it will be
>>> using some kind of hard threshold to decide which is which, in which case
>>> it's possible to make scenarios which will fall on the wrong side of the
>>> threshold naturally, and in which there could be subgroups whose only way
>>> to fix things would be favorite betrayal; or it will be resolving things by
>>> placing the strategic burden on the voters.
>>>
>>> One idea which I'd like to explore, but haven't managed to make work
>>> (yet?), is that of "patching FBC". For instance: take a sysem like PAR or
>>> PAR-prime, and restore FBC by making some way to cast a ballot that
>>> essentially says "these are my true preferences, but I realize that in
>>> order to get the best outcome I may have to help deep-six my true
>>> favorite". Since the true favorite would still be at the top, and since the
>>> "help eliminate my favorite" would only kick in if it actually helped, this
>>> would technically restore FBC.
>>>
>>> Another avenue that might be useful is to develop some weakened FBC
>>> criterion. For instance: "If the other ballots combined with your true
>>> preferences do not include a Condorcet cycle, there is always a
>>> strategically-optimal semi-honest ballot". In other words, if there isn't
>>> an honest CC, there's no motive to create a false one. I'd call this
>>> criterion "non-paradoxical semi-honesty". This is not exactly strictly
>>> weaker than FBC, but in practice it mostly is; most FBC-compliant methods
>>> would pass this criterion. But are there any non-FBC methods which meet it?
>>>
>>> ....
>>>
>>> OK, here's a proposal. It's PAR-like, it solves the same problem as
>>> PAR-prime does, but it may be technically FBC compliant:
>>>
>>>
>>>    1. Voters can Prefer, Accept, or Reject each candidate. Default is
>>>    Accept. For each candidate they prefer, they may also check a "secret"
>>>    checkbox.
>>>    2. Candidates with a majority of Reject, or with under 25% Prefer,
>>>    are eliminated, unless that would eliminate all candidates.
>>>    3. Candidates with a majority of (public reject plus secret prefer),
>>>    or with under 25% public prefer are given the label "supposedly
>>>    eliminated", unless all candidates would be "supposedly eliminated".
>>>    4. Each candidate gets a point for each ballot where they don't fall
>>>    below any non-supposedly-eliminated candidates. Most points wins.
>>>
>>>
>>> I think this may meet FBC, if you count secret preference as a kind of
>>> preference. Basically secret preference is a way of saying "I think I may
>>> be on the losing wing of a center-squeeze situation, but that the opposite
>>> wing may not be eliminated. Thus, I want the other voters on my wing to be
>>> ready to compromise, even if our candidate is apparently viable."
>>>
>>> This has all the good characteristics of PAR, except for the additional
>>> complexity it brings.
>>>
>>> Secret preference would not be a favored strategy in any simple
>>> 3-faction scenario; in fact, I think that it requires a minimum of 4
>>> factions AND 4 "meaningful" candidates (candidates without whom some
>>> ballots would not be using the full ratings range). If no candidate can be
>>> alone at bottom-rank unless they're alone at top rank for some faction, it
>>> may even take at least 5 factions before "secret" is ever a factor.
>>>
>>> In other words: secret preference is only a hacked-up patch to restore
>>> FBC, and not something that I think would be strategically useful in real
>>> life.
>>>
>>> ...
>>>
>>>
>>>
>>> ----
>>> 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/20161105/603d637f/attachment.htm>