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Forest Simmons | 1 Jun 2003 02:16
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Manipulability


On Sat, 31 May 2003, [iso-8859-1] Kevin Venzke wrote:

>  --- Alex Small <asmall <at> physics.ucsb.edu> a écrit :
> > MCA is also more likely to elect A in this scenario.  The A>B>C faction
> > can safely rate A preferred and B acceptable, unless they believe a
> > majority of the electorate is rating both B and C as preferred.  So while
> > MCA is not completely immune to manipulation of polls (is anything?), it's
> > certainly more robust than some methods.
>
> Looks that way.  A supporters who think A could have a majority might even
> disapprove B.  However, if they think C might have a majority of "preferred"
> ratings, they might bump B up to "preferred" along with A.  This scenario
> seems more likely than what you envisioned.
>

...

>
> I want to consider the case with three-rank Conditional Approval (of interest
> only to me, perhaps):
>
> Sincere:
> 6000 A>>B>C
> 3000 C>B>>A
> 1000 B>C>>A
>
> False poll:
> 35% A>B>C
> 40% C>B>A
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Kevin Venzke | 1 Jun 2003 08:29
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Re: MCA, 3RC, Pair Approval, Manipulability

Forest,

 --- Forest Simmons <fsimmons <at> pcc.edu> a écrit :
> > Question: What advantage does MCA have over three-rank Condorcet?
> >
> 
> Good Question!
> 
> I think it's easier to explain to the lay voter: "If nobody's favorite
> gets more than fifty percent of the votes, then the most acceptable
> candidate wins."
> 
> We need to compare the two methods on more examples to clarify the other
> advantages and disadvantages.

I thought a bit about my question after posting it, and these reasons
occur to me:
1. MCA is so close to Approval that it's almost a two-rank method.  Thus if
it's agreed that two-rank Condorcet (Approval) is better than three-rank 
Condorcet, then MCA should be better for those same reasons, whatever they are.
2. It's easier to explain, as you said.
2. Three-rank Condorcet requires a cycle-breaker of some kind.  That raises
the question of which it should be, and makes it even harder to explain.

Advantages of 3RC over MCA:
1. I'm worried that less savvy voters will fill out an MCA ballot like
it was a 3RC ballot.  In other words, that they will put unduly lousy
candidates in the second rank.
2. The expectation from ordering two candidates is the same no matter which
two ranks you place them in.  In MCA, A>B>_, A>_>B, and _>A>B all have
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Forest Simmons | 4 Jun 2003 01:57
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Re: MCA, 3RC, Pair Approval, Manipulability


On Sun, 1 Jun 2003, [iso-8859-1] Kevin Venzke wrote:

> Forest,
>
>  --- Forest Simmons <fsimmons <at> pcc.edu> a écrit :
> > > Question: What advantage does MCA have over three-rank Condorcet?
> > >
> >
> > Good Question!
> >
> > I think it's easier to explain to the lay voter: "If nobody's favorite
> > gets more than fifty percent of the votes, then the most acceptable
> > candidate wins."
> >
> > We need to compare the two methods on more examples to clarify the other
> > advantages and disadvantages.
>
> I thought a bit about my question after posting it, and these reasons
> occur to me:
> 1. MCA is so close to Approval that it's almost a two-rank method.  Thus if
> it's agreed that two-rank Condorcet (Approval) is better than three-rank
> Condorcet, then MCA should be better for those same reasons, whatever they are.
> 2. It's easier to explain, as you said.
> 2. Three-rank Condorcet requires a cycle-breaker of some kind.  That raises
> the question of which it should be, and makes it even harder to explain.

Excellent points.

>
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Kevin Venzke | 8 Jun 2003 23:24
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Re: Fwd: Is Condorcet The Turkey?

> Hello List
> 
> Recently there have been a large number of postings regarding something 
> called the turkey problem- indifferent/poor candidates winning as the least worst 
> choice in a condorcet ballet.

Yes, but I think we all still like Condorcet.

> Due to the nature of the Condorcet method- which considers lower preferences 
> before the fate of higher preferences is decided- condorcet would appear to me 
> to be a turkey electoral system.

How about "system with potential to elect turkeys."

> The fundamental difference as regards the results between condorcet and 
> irving is that  condorcet allows the election of candidates of candidates with 
> little or no first or higher preference support. It is these candidates who are 
> likely to be the turkeys.

Yes, but IRV is an extreme solution to this.  Plurality would plug the hole,
too.  There are plenty of ways to address Condorcet's turkey problem, if
it is perceived to be a problem: "None of the Below" option, approval cutoff
and threshold, limited ranks (e.g., with three ranks, it is guaranteed that a
CW was at least ranked in the middle by some people), count first-place
rankings (or those above an approval divider) as double opposition in the 
pairwise matrix...

> Candidate C does nothing, says nothing and offends nobody.

If C is basically invisible, I don't think the number of people voting
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Bart Ingles | 9 Jun 2003 08:15
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Re: Fwd: Is Condorcet The Turkey?


Kevin Venzke wrote:
> 
> Yes, but I think we all still like Condorcet.

I'm not crazy about it.  In a ranked election to choose an election
system I might rank it above "Irving", but in an approval election I
would likely bullet vote for approval voting.

Bart
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Kevin Venzke | 9 Jun 2003 23:38
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Re: Fwd: Is Condorcet The Turkey?

 --- Bart Ingles <bartman <at> netgate.net> a écrit : > 
> 
> Kevin Venzke wrote:
> > 
> > Yes, but I think we all still like Condorcet.
> 
> I'm not crazy about it.  In a ranked election to choose an election
> system I might rank it above "Irving", but in an approval election I
> would likely bullet vote for approval voting.

Sorry for speaking for you (and anyone else).  I was just thinking that,
within the "turkey" thread, it didn't seem like anyone was actually
saying Condorcet was bad.

I take it you prefer Approval because it requires its winners to be overtly
"approved" on ballots?

Kevin Venzke
stepjak <at> yahoo.fr

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Forest Simmons | 12 Jun 2003 21:01
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Re: IRV's Top Preferences Considered First Feature


On Thu, 12 Jun 2003, Forest Simmons wrote:

> Indeed artificial ballot constraints tend to elicit insincere ballots.

Note how Approval shines in this regard:

An Approval ballot may be considered as an unconstrained plurality ballot.

At a more subtle level Approval may be considered a CR ballot in which all
votes are constrained to the extremes of the ratings range. But it turns
out that this constraint is not artificial since it precisely conforms to
the dictates of optimal CR strategy regardless of the amount of
information available.

Note, however, that there are other uses for CR ballots than the standard
CR method of giving the win to the candidate with the highest average
rating.  In some of these other uses, including approval runoff,
constraining to the extremes is not in general consistent with optimal
strategy.  In this context this constraint would be almost as artificial
as the IRV and Coombs constraints.

Forest

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Kevin Venzke | 13 Jun 2003 19:51
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Re: Is Condorcet The Turkey?

 --- Dgamble997 <at> aol.com a écrit : 
> Kevin Venzke Wrote
> 
> In other words, campaigns become about personality instead of policy. I
> don't think that's necessarily a bad thing. Whatever policies the elected
> representatives enact, they still need to get reelected.
> 
> I have to disagree with this . Campaigns about personality as opposed to 
> policy tend to descend into trivial, sensational and hypocritical debate about 
> candidates private lives in general and sexual conduct in particular. Take for 
> example the unedifying spectacle of the Monica Lewinsky affair.

I believe you said you're familiar with politics in Britain, so I wonder if
this is why you say this.  I'm talking about the voters' "gut feel" about a
candidate, not the candidates' personal lives.  This plays a big (bigger?)
role in U.S. elections.

> 
> Kevin also wrote
> 
> I think "compromise at any cost" is a good strategy for electing the members
> of a legislature. Policies supported by a majority vote of compromises should
> be pretty reasonable. But if you elect lop-sided candidates, chances are you
> will get lop-sided results. That is what I want to avoid "at any cost," and
> compromise at the election level appears to be the solution.    
> 
> You say lop-sided I say decisive and radical when decision and action are 
> necessary.

Yes, but if lop-sided in the other direction, exactly the opposite decisions
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Forest Simmons | 14 Jun 2003 02:22
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Re: Is Condorcet The Turkey?


On Fri, 13 Jun 2003, [iso-8859-1] Kevin Venzke wrote in response to the
first paragraph (marked with > > below):

>
> > Motives and situations that encourage insincere voting can be found under
> > virtually any electoral system Condorcet being no exception.
>
> True, but that doesn't mean all methods are equal in this regard.
>

And Condorcet is much better than IRV for reasons that I have tried to
elucidate in recent postings.  See Steve Eppley's web page for additional
explanations of why his version of Ranked Pairs is about as close as you
can get to the ideal.  You'll search in vain for anything approaching that
quality of analysis by IRV supporters.

One more thought on IRV's exhausting of higher options before considering
lower ones:

Remember IRV proceeds by elimination.  It seems to me that when deciding
whom to eliminate we should start with the lower ranking candidates, and
that lower ranking candidates can be determined from the bottoms of the
ballots at least as well as from the tops of the ballots.

Forest

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Forest Simmons | 14 Jun 2003 02:34
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Re: IRV's Top Preferences Considered First Feature

Just to be clear, although approval runoff is uniformly better than (one
of its constrained versions) IRV, approval runoff is inferior to Approval,
because like any method that proceeds by elimination, it is susceptible to
insincere order reversals, while Approval is not.

Of course, Approval's simplicity clinches its superiority over approval
runoff.

Most of us on this EM list agree that no other method as simple as
Approval improves on Approval, and it's hard to find a more complicated
method whose additional complication is justified by some supposed
advantage over Approval.

MCA might barely fulfill the requirement.

Forest

On Fri, 13 Jun 2003, Forest Simmons wrote:

> I'm not advocating approval runoff, only using it as a method that can be
> easily compared with IRV, because IRV can be thought as a special case of
> approval runoff where the ballots are constrained, just as plurality can
> be thought of as a special case of approval in which the voters are
> constrained to mark only one candidate, otherwise resulting in a spoiled
> ballot.
>
> True, Approval doesn't allow you to rank the candidates, but that would be
> impossible with a plurality style ballot, whereas Approval is possible is
> with that style ballot.
>
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