[EM] Anti-defection strategy device for IBIFA

[Michael Ossipoff]

I'd said that, like 3-Slot ICT, Conditional Bucklin doesn't let you give
full protection to the distrusted voters candidate, or to any candidate
that you merely approve, because you aren't helping hir get a majority.

But then, in a later posting, i said that the favorite-designation
shouldn't give anything in the points-count, because that would create a
strategic need to give that favorite designation to a compromise, or to the
distrusted voters' candidate.

So the favorite designation would be distinct from the ratings that give
points, such as an Approval ballot, or the 1st rank of a Bucklin ballot.

Well, my 2nd comment fixes the problem that I mentioned in my 1st comment.

Have a favorite-designation that doesn't count for points in any way, and
whose only use is for determining whether the conditional approval should
be given.

Below that is the Approval ballot, or the Bucklin ballot, starting with its
1st rank position.

Then, the method is Conditional Approval, or Conditional Bucklin, with a
favorite-designation used only for determining whether the conditional
approval will be given.

In Conditional Buckllin,  every vote given by a ballot, at every stage of
the count (or every vote other than the the one given in the 1st round),
can be conditional, if the voter so marks it.

A special case of that would be 3-Slot Conditional Bucklin, in which, in
addition to the favorite-designation, the ballot has a 3-Slot Bucklin ballot

As I said last night, at any particular round of Conditional Bucklin, the
conditional vote would be given if the vote-receiver's vote total, just
before that round is greater than that of the giving ballot's designated
favorite with the highest vote total at that time.

But maybe it would be better to only allow a ballot to designate one
favorite, partly to simplify the count rule, shortening the definition,
making it easier to propose.

So: Conditional Approval, or Conditional Bucklin--which would include
Conditional 3-Slot Bucklin.

As I said, no doubt Chris's improved interpretation of majority is indeed
an improvement, but it's too complicated for a first reform from Plurality.
It would be a good refinement for later.

When there are two or more candidates getting a majority in a round, or
when there are no majorities at the end of the count, I prefer declaring
the winner based on vote-total, rather than top-count.

For one thing it results in a briefer definition.

And it makes the votes given at the various non-top stages of the count
more effective, which seems more in keeping with Bucklin's purpose..

And it chose D in Forest's example that I was discussing last week.

I understand that using the top-count instead of the vote-total helps the
chicken dilemma situation some, but it doesn't eliminate the chicken
dilemma..That's especially ok if the chicken dilemma problem is eliminated
by Chris's conditional vote option.

Michael Ossipoff


On Thu, Nov 3, 2016 at 8:53 AM, C.Benham <cbenham at adam.com.au> wrote:

> I normally don't like explicit strategy devices, and (beyond considering
> it desirable to elect from the
> voted Smith set) don't care very much about the "center squeeze" effect.
>
> (I like truncation resistance, so I'm happy with some of the methods that
> meet the Chicken Dilemma criterion.)
>
> Nonetheless here is  version of  IBIFA with a device aimed at addressing
> the Chicken Dilemma scenario.
>
> * Voters mark each candidate as one of  Top-Rated, Approved, Conditionally
> Approved, Bottom-Rated. Default is Bottom-Rated.
>
> A candidate marked "Conditionally Approved" on a ballot is approved if hir
> Top Ratings score is higher than the highest
> Top Ratings score of any candidate that is Top-Rated on that ballot.
>
> Based on the thus modified ballots, elect the 3-slot IBIFA winner.*
>
> ("Top-Rated"  could be called 'Most Preferred' and "Bottom-Rated" could be
> called 'Unapproved' or 'Rejected').
>
> To refresh memories, IBIFA stands for "Irrelevant-Ballot Independent
> Fall-back Approval", and the 3-slot version goes thus:
>
> *Voters rate candidates as one of  Top, Middle or Bottom. Default is
> Bottom.  Top and Middle is interpreted as approval.
>
> If any candidate X  is rated Top on more ballots than any non-X is
> approved on ballots that don't top-rate X, then the X
> with the highest Top-Ratings score wins.
>
> Otherwise the most approved candidate wins.*
>
> http://wiki.electorama.com/wiki/IBIFA
>
> 35: C
> 33: A>B
> 32: B (sincere might be B>A)
>
> In the scenario addressed by the Chicken Dilemma criterion, if all  (and
> sometimes less than all) of A's supporters only "conditionally"
> approve B then the method meets the CD criterion.  Otherwise it meets the
> Minimal Defense criterion.
>
> http://wiki.electorama.com/wiki/Chicken_Dilemma_Criterion
>
> http://wiki.electorama.com/wiki/Minimal_Defense_criterion
>
> Of course it meets the Plurality criterion and doesn't have any
> random-fill incentive.
>
> The downside is that the use of  Conditional Approval can cause a
> vulnerability to Push-over strategy.
>
> 48: C
> 27: B
> 25: A>>B
>
> The A supporters are all only conditionally approving B, but that has the
> same effect as normal approval because B has a higher Top Ratings score
> than A.  But now if 3 to 22 of the C voters change to C=A  then A's  Top
> Ratings score rises above B's so the "conditional" approval is switched off
> and then C wins.
>
> I dislike this "at the same time"-no-help failure, but the new result
> doesn't look terrible and of course if the B voters really prefer A to C
> then
> they were foolish not to conditionally approve A. If they'd done that then
> the attempted Push-over would have just elected A.
>
> (It crossed my mind to try to make Push-over strategising  more difficult
> and riskier with the same mechanism I suggested a while ago for IRV
> or Benham that allows above-bottom equal-ranking, but that would have
> broken compliance with FBC.)
>
> Chris Benham
>
>
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