Re: [EM] Critique of FairVote's "approval voting" report

[Jameson Quinn]

The critique now has a number of comments in the margin, from a number of
people, including responses from Rob Richie (probably the original author of
the report). At the bottom, I've added my critique of the pervasive error
Fairvote (Richie?) makes. Here is a copy of my critique:

Strategy in Approval: the real story

In order to understand what the effect of “strategic” approval voting is, we
must first have some definition of “honest” approval voting to compare it
against. Various definitions are possible:

   1.

   Approve any candidate who’s better than the average serious candidate.
   -

  This is close to perfect strategy, so while it’s a fair definition of
  “honest”, we can’t really use this as a basis for comparing how
much of an
  advantage strategy gives. To do so could be criticized as biased
in favor of
  approval.
  2.

   Bullet vote. That is, approve only a single candidate.
   -

  This is apparently Fairvote’s (mistaken) idea of a strategy, so I
  guess we can’t use this as a basis for comparison either.
  3.

   Anti-bullet vote. That is, approve all but a single candidate.
   -

  This is a stupid strategy, and one which most people, who tend to be
  partisan and tribal, would not naturally tend to use. I only mention it
  because it’s the definition of “honest” used by Tideman. We will
not use it
  here.
  4.

   Set your approval threshold arbitrarily, somewhere in between your
   favorite and least-favorite candidate, and approve everyone above the
   threshold.
   -

  Obviously, people will be more likely to approve of a candidate the
  more they like that candidate. With enough voters, the law of
averages will
  even out the randomness of the arbitrary decisions, and so the
system will
  become roughly equivalent to range voting. (Technically speaking, it
  will be range voting, with the true range vote passed through some
  monotonically increasing, probably roughly integral-sign-shaped,
probability
  function; and with some slight random noise proportional to the
square root
  of the number of voters, around 0.1% for a million voters).

   Since definitions 1 and 2 could be called biased in favor of approval
   voting, and definition 3 is just stupid, we’ll use definition 4 for the rest
   of this analysis.

   Note that under definition 4, the honest approval winner is just the
   honest range winner. That has been shown to be the system which comes
   closest to electing the true utility winner for the voters - the winner who
   makes the average voter happiest. So this is an excellent result for honest
   approval.

   So, what about strategy? Is it true, as Fairvote claims, that “strategic
   voters will always earn a significant advantage over less informed voters”?
   Well, that depends what you mean by “strategy”.

   Let’s start by trying Fairvote’s definition:

   “...[V]oters who vote tactically by casting a single vote for their
   favorite candidate will gain an advantage over those voters who indicate
   support for more than one candidate”

   This is totally false. Such voters will only gain an advantage if their
   favorite candidate wins. On the other hand, they will be hurting themselves
   if they happen to have favored the candidate who ends in second place, over
   the candidate who ends in first place. In a 5-candidate election, they gain
   in an average of about 20% of the cases, and lose in an average of about
   40%; that is, they lose on average of about twice as often as they gain.
   Since this is not even advantageous, Fairvote is flatly incorrect to
   repeatedly claim that bullet voting is even “strategic”, let alone
   “always... a significant advantage”.

   What about other strategies? Correct Approval strategy is, approximately,
   to set your approval threshold at the average quality of the candidates whom
   you think might win. Unless the election is abnormally close, only two
   candidates have a real chance of winning, and of those two one is clearly
   leading, so that means you should approve one of the two frontruners and
   everyone you like better.

   This strategy, unlike Fairvote’s false “strategy”, does indeed give the
   voter a significant advantage. Since, as we’ve seen, our definition of
   honest Approval voting is probabilistically equivalent to Range voting, the
   advantage for strategic voting is the same as it would be in Range. This is
   in fact “always ... a significant advantage”. However, several things should
   be noted:
   -

  The actual advantageous strategy is precisely the opposite of the
  so-called “strategy” which Fairvote claims will be the pervasive problem
  with Approval.
  -

  If everyone uses their best strategy, the winner will be the Condorcet
  winner, if one exists. Far from being a problematic or
pathological result,
  this is seen by many as the most democratic result for the

Re: [EM] Critique of FairVote's "approval voting" report

[Kristofer Munsterhjelm]

robert bristow-johnson wrote:

dunno if i can do much critiquing of that particular doc.  what i
like is in FairVote's page:

http://www.fairvote.org/single-winner-voting-method-comparison-chart


where they claim that IRV will do a better job getting the Condorcet
winner than does Condorcet (sometimes the Condorcet method will
*fail* to elect the Condorcet winner for those who didn't know that):

"IRV will generally elect a Condorcet winner, ... IRV may actually do
a better job of electing Condorcet winners that nominal Condorcet
voting methods, because of the incentives for strategic voting under
Condorcet rules that are absent under IRV. ... Condorcet voting is
designed specifically to find and elect a Condorcet winner whenever
such a candidate exists. Ironically, due to incentives for strategic
voting inherent in Condorcet methods, they may in fact fail to elect
the Condorcet winner, even when one exists."

i know, so up is down, black is white, etc.


It's not so surprising that they claim this. They can't claim that IRV 
passes Condorcet, because it's an easily demonstrable fact that IRV 
doesn't - any ballot set that leads to IRV electing a different 
candidate than the CW constitutes a proof that IRV fails the Condorcet 
criterion.


Therefore, they have to focus their efforts along two lines: that the 
Condorcet criterion is undesirable and so that IRV failing Condorcet is 
a *good* thing, or that while the letter-of-the-law is that IRV fails 
Condorcet, if one alters the playing field, then the situation changes 
to the benefit of IRV.


The first approach is done through emphasis on "weak winners" and 
"Condorcet winners that are nobody's favorite", "core support", and 
similar objections. FV asks us to envision a flip-flopper that is bland 
enough to not be greatly disliked and so wins even though nobody liked 
him, either, and then they imply that if you choose a Condorcet method, 
that's what you'll get.


The second approach is what you see here. By redefining the playing 
field to be "in the case of strategic voters", they can say that IRV 
passes Condorcet and does so even more often than does ordinary 
Condorcet methods. Even if that doesn't hold, it's no longer a matter of 
outright fact any more - simulating strategic behavior is hard and so 
they might claim that IRV elects Condorcet winners more often under 
certain models, and then redirect the argument to a more exotic one 
about which models are "realistic".


I don't even think the claim is correct. If strategy resilience makes 
IRV elect Condorcet winners more often than Condorcet, and JGA's paper 
suggests one can preserve IRV's strategy resistance while also getting 
Condorcet (by prefixing IRV with logic that turns it Condorcet 
compliant), then it is not at all clear that the Condorcet-IRV methods 
would rarely elect true Condorcet winners. Both of the methods JGA 
investigated resisted simple strategy better than did the "unadorned" IRV.


Incidentally, Rob Richie commented (on the discussion page for Approval 
voting on Wikipedia) that to consider restricted situations where 
Approval voting would pass certain criteria it otherwise would not, only 
muddied the waters and so shouldn't be done. Yet, this "more CW than 
Condorcet" seems to do something similar: one considers a voting method 
over a limited subset of voting behavior, and then states that the 
method passes a certain criterion (which it might, given the limited 
subset) that it otherwise would not.


(Also, FairVote is simply wrong when they say "Only the plurality, 
two-round runoffs and IRV have ever actually been used in U.S. 
governmental elections". If they only consider national/presidential 
elections, then neither top-two nor IRV has been used; and if they 
consider local elections, too, then Nanson's method, which they consider 
a Condorcet method, has been used.)



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Re: [EM] Critique of FairVote's "approval voting" report

[robert bristow-johnson]

dunno if i can do much critiquing of that particular doc.  what i like is in 
FairVote's page:

  http://www.fairvote.org/single-winner-voting-method-comparison-chart 

where they claim that IRV will do a better job getting the Condorcet winner 
than does Condorcet (sometimes the Condorcet method will *fail* to elect the 
Condorcet winner for those who didn't know that):

"IRV will generally elect a Condorcet winner, ... IRV may actually do a better 
job of electing Condorcet winners that nominal Condorcet voting methods, 
because of the incentives for strategic voting under Condorcet rules that are 
absent under IRV.
...
Condorcet voting is designed specifically to find and elect a Condorcet winner 
whenever such a candidate exists. Ironically, due to incentives for strategic 
voting inherent in Condorcet methods, they may in fact fail to elect the 
Condorcet winner, even when one exists."

i know, so up is down, black is white, etc.


--

r b-j  r...@audioimagination.com

"Imagination is more important than knowledge."

-Original Message-
From: "Jameson Quinn" [jameson.qu...@gmail.com]
Date: 10/10/2011 18:26
To: "electionsciencefoundation" , "EM" 

Subject: [EM] Critique of FairVote's "approval voting" report

I would like to make a detailed critique of the FairVote report theyve put up 
at approvalvoting.blogspot.com and rangevoting.com. I believe that every single 
one of the conclusions of that report is dangerously wrong. Ive created a 
google doc to help make this critique collaboratively. Please add comments to 
the doc to help critique.

Thanks,
Jameson


Election-Methods mailing list - see http://electorama.com/em for list info

[EM] Critique of FairVote's "approval voting" report

[Jameson Quinn]

I would like to make a detailed critique of the FairVote report they've put
up at approvalvoting.blogspot.com and rangevoting.com. I believe that every
single one of the conclusions of that report is dangerously wrong. I've
created a google
docto
help make this critique collaboratively. Please add comments to the
doc
to help critique.

Thanks,
Jameson

Election-Methods mailing list - see http://electorama.com/em for list info