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

[C.Benham]

The "deweight  to zero" option would be best for avoiding an extra easy 
Push-over incentive.

With voters being allowed to rank both above and below an approval 
threshold, this a one-ballot per voter and one trip
to the polling station version of an earlier suggestion of mine for a 2 
trips to the polling station method using simple Approval
ballots.

But then we have a method that can badly fail Condorcet and fails FBC.

I suppose if  we don't mind a kludge fix it to meet Condorcet:

*Voters submit rankings with an approval threshold (Default is all 
candidates ranked above equal-bottom are interpreted as approved).
Elect the CW if there is one.
Otherwise elect the pairwise winner between (among members of the Smith 
set?)  the most approved candidate A and the candidate
most approved on ballots that don't approve A.*

Chris Benham



On 11/12/2016 10:51 AM, Forest Simmons wrote:
> 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 <mailto: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 <mailto: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.
>         ----
>         Election-Methods mailing list - see http://electorama.com/em
>         for list info
>
>
>
>
>
> ----
> 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/20161112/964548e8/attachment-0001.htm>