[EM] Top-two Approval Pairwise Runoff (TTAPR)

[Monkey Puzzle]

In this chicken dilemma defection situation, the As and Bs could add
preferences below the approval cutoff:

40 C
32 A>>B
28 B>>A

Both groups defect from each other, but assign their rival a higher
preference above other disapproved candidates.

C and the larger first choice of A or B are the two parliament seats, and
the disapproved preference helps that candidate win.

 Frango ut patefaciam -- I break so that I may reveal

On Fri, Nov 11, 2016 at 12:21 AM, Kristofer Munsterhjelm <
km_elmet at t-online.de> wrote:

> On 11/11/2016 01:48 AM, Forest Simmons wrote:
> > Some of the replies are taking the subject line too literally.  We're
> > not talking about top two runoff, but two member PR runoff.  we find out
> > who the two member parliament would be then pit those two against each
> > other.
> >
> > So
> >
> > 40 C
> > 32 A>B
> > 28 B>A
> >
> > Suppose that we use PAV with implicit approval
> >
> > The A is the first member in the two member parliament.
> >
> > The two factions that supported A get their weights cut in half, so C is
> > the second member.
> >
> > The runoff is between A and C, not between A and B, as some people are
> > assuming.
> >
> > If the B faction defects, then the two members of the pariliament would
> > be B and C, and the pairwise winner would be B, so the method does not
> > satisfy CD.
>
> On a more intuitive level, that isn't too surprising. Suppose you have a
> Bush-Nader-Gore situation. The runoff doesn't help the voters who want
> to know whether to vote {Nader, Gore} or {Nader}, since if they vote
> only Nader, Bush and Gore may go to the runoff (i.e. Nader loses). On
> the other hand, if they do vote {Nader, Gore}, and Gore is picked for
> the first winner, then their ballots will be deweighted and Nader
> probably won't come in second anyway.
> ----
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>
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