# [EM] Re: Strong FBC at last! ....Approval Runoff

Chris Benham chrisbenham at bigpond.com
Thu Apr 3 21:14:01 PST 2003

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-------- Original Message --------
Subject: Re: Election-methods digest, Vol 1 #63 - 3 msgs
Date: Fri, 04 Apr 2003 13:05:32 +0930
From: Chris Benham <chrisbenham at bigpond.com>
To: election-methods-electorama.com at electorama.com, asmall at physics.ucsb.edu
References: <20030403200213.30036.18824.Mailman at geronimo.dreamhost.com>

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>On Thu, 3 Apr 2003, Chris Benham wrote:
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>From: "Alex Small" <asmall at physics.ucsb.edu>
>To: <election-methods at electorama.com>
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>On Thu, 3 Apr 2003, Chris Benham wrote:
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>>Forest,
>>My answer to your question "Is there a simpler method that factors
>>all of the strategy away from the rankings or ratings of the
>>candidates?" is yes. Voters can rank  and also Approve whichever
>>candidates they please, not even neccessarily approving the candidate
>>they rank as number1. The method  is to have an IRV-like count, except
>>that the candidates who are in turn eliminated are those who are the
>>least approved.
>>For example, in a 3 candidate race in which you doubt that  Favourite
>>can beat Worst  in a runoff, you might number the candidates  1.
>>Favourite  2. Middle  3. Worst  , but  only  Approve Middle .
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>Is this any different from Approval Runoff, where you eliminate all but
>the two most approved candidates in the first round, and the second round
>is a single pairwise contest?
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Chris Benham:   Yes, completely different.

>  I ask because you say "the candidates who
>are eliminated in turn...", which (to me) implies a sequential process.
>I'm trying to see how you can get a sequential process only using approval
>information.
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Chris Benham:  I don't see how you can, but in this case we also have
the candidates ranked in order of preference information.

>It seems like the key insight needed for Strong FBC is that Strong FBC can
>only be satisfied when rankings are only used to resolve a single
>2-candidate contest.
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>So, if we use a rated method to eliminate all but 2 candidates, we can
>then use the rankings without any incentive to rank insincerely.
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>One interesting thing about Approval Runoff is that strategically it
>satisfies the Majority Criterion:  When there is a candidate whom a
>majority of the voters consider their first choice then he should win.
>With adequate polling data, the majority will be aware of one another, and
>they'll approve only their favorite.  He's guaranteed to be one of the top
>2, and he'll also automatically win the pairwise contest.
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C.B:  "With adequate polling data" plain Approval  and even Plurality
are ok in this respect.

>One possible downside:  The largest single organized group of voters (not
>necessarily a majority, nor a group that has a common favorite) can
>guarantee a candidate's victory by only approving him and a freak.  If
>their favorite is a serious candidate he'll automatically beat the freak
>in a pairwise contest.
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C.B: This version of  Approval Runoff  is hopeless. If each of the
competitive parties fields only one candidate,
then the first round will  be dominated by strategy. Voters who want to
maximise the chances of their favourite
will approve their favourite plus candidates that they think their
favourite can beat (as in your example).
Voters who think that their favourite can't win and whose main concern
is to stop Worst, will approve only those
acceptable candidates who they think can beat Worst, not neccessarily
including their favourite.
If a party thinks that it can win the first round, then it can just
field two candidates.

Chris Benham

>Alex
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>End of Election-methods Digest
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