[EM] two new hybrid approval-ranking methods by Brams & Sanver

[Kevin Venzke]

Hello,

--- Warren Smith <wds at math.temple.edu> a écrit :
> On Brams' web page
> http://www.nyu.edu/gsas/dept/politics/faculty/brams/brams_home.html
>  is found
> Steven J. Brams & M. Remzi Sanver:
> Voting Systems That Combine Approval and Preference,
> Dec 2005.
> 
> This paper introduces two new hybrid approval-preference voting systems.
> 
> I. Preference-Approval-Voting:

I wonder why he gave it this name. "PAV" is an over-used acronym. It's
also like he doesn't know that other rank+approval methods have been
invented (such as Woodall's "Approval AV") which could merit this
name.

To be descriptive I would call this method :

Majority Approval//Condorcet//Approval.

("Majority Approval" here has to mean that if no candidate has majority
approval, the most-approved candidate wins.)

I'm not very happy with this claim:

"A majority-preferred [i.e., pairwise] candidate is likely to have a
more coherent point of view than an AV [approval] winner, who may be
the most popular candidate because he or she is bland and inoffensive--
a kind of lowest common denominator who tries to appease everybody.
*Not* choosing such a candidate makes PAV *coherence-inducing for
candidates*
by giving an advantage to candidates who are principled but, nevertheless,
command broad support."

They're claiming that a majority-approved candidate who pairwise defeats 
all other majority-approved candidates is "likely to have a more coherent 
point of view" than the candidate who simply had the most approval.

They never say *why* a pairwise winner would have a "more coherent 
point of view" than an approval winner. That could get its own paper.

Also, this characterization of approval winners is not what I would
expect from an approval advocate.

> II. Fallback-Voting:
> 
> WDS comments:
> It appears that "fallback voting" is a
> rediscovery of "Bucklin voting" which was used to elect governors in
> several US states,
> with ballot-truncation being allowed.
> See  http://wiki.electorama.com/wiki/ER-Bucklin 
>      http://wiki.electorama.com/wiki/Bucklin_voting
> Oddly, Brams & Sanver were aware of Bucklin but seem to think their
> method is different.
> I don't really see why.

Sanver was apparently involved in writing an article about "the
majoritarian
compromise," which according to this article differs only in that this
method doesn't allow truncation.

I get the feeling they weren't aware of Bucklin. The article says that
the only difference between Bucklin and FV is that Bucklin doesn't 
assume approval of ranked candidates!

Since approval isn't used in either method, Bucklin == FV.

> Also strangely, B&S do not consider ER-Bucklin,
> which is
> quite an interesting system since it avoids "favorite betrayal."  

I imagine they would care about satisfying clone independence before
they'd think of FBC.

The footnote on page 36 shows a misunderstanding of the FBC methods.
MDDA (not named) is described correctly, but the authors dismiss it
because they believe this means the Condorcet winner always wins. That
is more similar to ICA.

Also, they don't refer to FBC at all, which makes one wonder why they
chose the FBC survey of methods rather than some other survey.

Kevin Venzke



	

	
		
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