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

[Forest Simmons]

Very good!  And it works for a variety of Proportional Representation
methods, whether you deweight the ballots to 1/2, 1/3, or even totally
deweight to zero, so that no ballot that approved the first finalist has
any weight at all in deciding who the second finalist is.  That may be the
simplest method.


On Fri, Nov 11, 2016 at 10:13 AM, Monkey Puzzle <
araucaria.araucana at gmail.com> wrote:

> 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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>> info
>>
>
>
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