[EM] Three rounds

[Juho Laatu]

--- On Mon, 10/11/08, Raph Frank <raphfrk at gmail.com> wrote:

> From: Raph Frank <raphfrk at gmail.com>
> Subject: Re: [EM] Three rounds
> To: juho4880 at yahoo.co.uk
> Cc: election-methods at lists.electorama.com
> Date: Monday, 10 November, 2008, 7:59 PM
> On Mon, Nov 10, 2008 at 4:05 PM, Juho Laatu
> <juho4880 at yahoo.co.uk> wrote:
> > One could e.g. force supporters of the
> "eliminated" candidates to approve more than one
> candidate (at least one of the "remaining"
> candidates) (instead of just bullet voting their second
> preference). On possible way to terminate the algorithm
> would be to stop when someone has reached >50% approval
> level.
> >
> > Also in "non-instant" runoffs one could e.g.
> force the voters to approve at least one on the
> "remaining" candidates. (One could eliminate more
> than one candidate at different rounds.)
> 
> That is kinda like Bucklin, though without the approval
> threshold
> changing in each round for all voters.
> 
> The process could be
> 
> 1) Each candidate is designated a strong candidate
> 2) Each ballot is considered to approve the highest ranked
> strong
> candidate and all candidates ranked higher.
> 3) If the most approved candidate has > 50%, then that
> candidate is elected.
> 4) Re-designated the least approved strong candidate a weak
> candidate
> and goto 2).

Yes, could go this way.

> 
> It still suffers from centre squeeze effects, though.
> 
> For example
> 
> 45: A>B>C
> 9: B>A>C
> 46: C>B>A
> 
> Round 1
> 
> A: 45
> B: 9
> C: 46
> 
> no winner, B designated 'weak'
> 
> Round 2
> 
> A: 54
> B: 9
> C: 41
> 
> A wins.

How about continuing and allowing the C supporters to compromise and approve also B. (Just didn't use the 50% termination rule this time.) After this round B would win and there would be no more interest to compromise (all voters already either approve the to be winner or would approve it as a compromise).

> 
> The method has potential strategic truncation incentives.
> 
> If B voters bullet voted for B, the result would have been
> 
> Round 2
> 
> A: 46
> B: 9
> C: 41
> 
> C designated 'weak'
> 
> Round 3
> 
> A: 46
> B: 55
> C: 41
> 
> B wins
> 
> Ofc, the other voters can use counter strategies.
> 
>  It might be worth adding a rule that if all candidates on
> a ballot
> are weak, the ballot counts as approving everyone.

Yes, short ballots like "B" would be seen as "B>A=C". The unlisted A and C candidates are at shared last position. B supporters are not allowed to refuse to compromise after B is declared "weak", so they have to approve both A and C.

Juho