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Rob Lanphier | 1 Apr 2003 07:44
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The "Tennesee example" for Condorcet

Hi all,

I came up with my new favorite example to demonstrate how Condorcet's 
method works, which I documented on Wikipedia.  The link is here:
http://www.wikipedia.org/wiki/Condorcet%27s_method

The idea is to simulate an election for the capital of the state of 
Tennessee, with the four candidates being Memphis, Nashville, 
Chattanooga, and Knoxville.  The distribution and geography of the state 
lend itself well to this comparison, since it's not too far removed from 
a single-dimensional "political spectrum" that people are used to 
thinking of, but it hints at the multidimensional facet, and is 
reasonably concrete.  At least, it's concrete if you have a map in front 
of you or if you really know Tennessee geography...as for me, I needed a 
map (though as a bonus, I know more about Tennessee geography than I 
knew 24hrs ago).

Rob

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James Gilmour | 1 Apr 2003 12:46
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RE: IRV in action

> On Sun, 30 Mar 2003 22:38:15 -0800 Rob Lanphier wrote:
> > Very interesting.  It's a shame they didn't post the individual ballots
> > in a way that a Condorcet tally could be run.

Yes, it would have been interesting (to us), but this was the election Result
Sheet, so such information was irrelevant and hence, not published.

> > This looks like a really strange example of an election.  The
> > candidate/voter ratio was extremely high, and presumably, the candidates
> > had an opportunity to establish a somewhat personal relationship with
> > all of the voters (especially the incumbent pre-reform peers, who they
> > presumably worked with in the "good old days").  Thus, it's not hard to
> > imagine why the rankings were so deep compared with what you might
> > expect in another type of election.

Yes, it was a VERY strange election - for all the reasons you state.
In my experience of counting IRV and STV-PR elections, I have found that the depth
of rankings does vary very greatly among voters, even when the number of
candidates is small.  Unless we ask them, we cannot know the reasons why such
voters do not use all their preferences, but I suspect there are several different
reasons.  Repeated exposure to X-voting in FPTP elections may have some effect on
UK electors.

> > It's also interesting how they chose to whittle down the number required
> > to win as ballots dropped off.  There were 423 ballots, where the first
> > column lists "Votes needed to be elected: 212".  However, by the time
> > you reach column 42, the votes needed to be elected drops to 134.  Is
> > this standard practice in IRV, or was this done to avoid the
> > embarrassing situation where no candidate in the runoff receives a
> > majority, even after receiving 42 rounds of ballot transfers?
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Forest Simmons | 2 Apr 2003 04:05
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The Strong Favorite Betrayal Criterion at Last!

This is the first day of April, but I'm really serious about the subject
line.

If I am not mistaken, it is indeed possible to satisfy the strong FBC with
the right kind of ballot, though it seems impossible with any ballot type
that has been proposed previously.

The ballot has two parts.  The first part is an ordinary ranked preference
ballot or a Cardinal Ratings ballot with enough resolution to distinguish
all of the candidates.

The second part must provide a way for each voter to mark (or leave
unmarked) as many pairs of candidates as desired.

The candidate pair receiving the most marks is the finalist pair.

The winner is the head-to-head winner of the finalist pair, i.e. the
member of the pair which is ranked or rated above the other on (the first
part of) the greatest number of ballots.

In summary, this method uses approval of pairs to pick the finalist pair,
and then uses the pairwise matrix compiled from the rankings or ratings to
determine which member of that pair is the method winner.

Since the first part of the ballot (the ranking or rating part) has no
influence on which pair of candidates is the finalist pair, there is
nothing to gain from insincere ranking or rating on that part of the
ballot.

All of the strategy is limited to the second part of the ballot.
(Continue reading)

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Dave Ketchum | 2 Apr 2003 19:43

Re: IRV in action

On Tue, 1 Apr 2003 11:46:44 +0100 James Gilmour wrote in part:

 >>On Sun, 30 Mar 2003 22:38:15 -0800 Rob Lanphier wrote:
 >
 >>>In this particular
 >>>election, there's no knowing how many of the 115 ballots accumulated by
 >>>Montgomery of Alamein (the runner up) in the 42nd round actually listed
 >>>Ullswater (the winner) next (who won with 151 votes).  If less than 61
 >>>ballots (i.e. 212 minus 151) of the 115 Montgomery of Alamein ballots
 >>>had listed Ullswater, then there was indeed no majority winner.
 >>>
 >
 >>Dave Ketchum replied
 >>Here you need to understand the language IRV uses - they LIKE the word
 >>"majority", treading lightly on the fact that they are doing a majority of
 >>the ballots that remain to be used to determine a winner, and not a
 >>majority of total ballots.
 >>
 >
 > See my comment above.  Whatever other defects it may have, IRV does 
ensure that
 > the winner has the support of half or more of those who are voting at 
the point
 > when the final decision is made.  If some voters choose to drop out 
before the end
 > point is reached, that is their choice.  No one should claim more for 
IRV than can
 > be justified, but equally those who don't like IRV should not 
misrepresent the
 > results.
(Continue reading)

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Adam Tarr | 2 Apr 2003 20:25
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RE: IRV in action

James Gilmour wrote:

>But the thinking behind the use of the word in this context is also 
>instructive.
>You have to remember that IRV is nothing more than a convenient method of
>condensing an exhaustive ballot into one voting operation.  (It also 
>avoids all
>the horse-trading that typically takes place between the successive rounds 
>of an
>exhaustive ballot, but that's a different issue.)

Some have argued that this "horse trading" allows compromise candidates to 
stave off defeat.

>See my comment above.  Whatever other defects it may have, IRV does ensure 
>that
>the winner has the support of half or more of those who are voting at the 
>point
>when the final decision is made.

The winner does have "the support of half or more of those who are voting", 
but only over the remaining candidates.  You can't overstate the 
significance of that.  Good candidates, candidates who have more support by 
any reasonable measure, can be discarded by IRV before a final decision is 
made.  Here's just such a "nightmare" example:

10% FarRight>Right>Centrist>Left>FarLeft
10% Right>FarRight>Centrist>Left>FarLeft
15% Right>Centrist>FarRight>Left>FarLeft
16% Centrist>Right>Left>FarRight>FarLeft
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Alex Small | 2 Apr 2003 20:50
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RE: IRV in action

Adam Tarr said:
> James Gilmour wrote:
>
>>But the thinking behind the use of the word in this context is also
>> instructive.
>>You have to remember that IRV is nothing more than a convenient method
>> of condensing an exhaustive ballot into one voting operation.  (It also
>>  avoids all
>>the horse-trading that typically takes place between the successive
>> rounds  of an
>>exhaustive ballot, but that's a different issue.)
>
> Some have argued that this "horse trading" allows compromise candidates
> to  stave off defeat.

I wonder if people will be more aware of the strategic aspects of runoff
voting if it is done with successive elections rather than a single round
(IRV).

Save we have 3 candidates, and in pairwise contests B>A, C>A, B>C.  If B
is running last in the count of first-place votes, we all know that IRV
gives individuals with the preference A>B>C to insincerely rank B first. 
Same for 2-step runoff (which is formally equivalent to IRV with 3
candidates, although not with 4+ candidates).

When is a voter more likely to think "I need to make sure my conquering
compromise makes it into round 2 rather than my doomed favorite":  IRV or
2-step runoff?  I don't claim to have an answer to that psychological
question, but it would be interesting if somebody has done that study.
(Continue reading)

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Alex Small | 2 Apr 2003 23:13
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Re: Re: Strong Favourite Betrayal Criterion at last!

On Thu, 3 Apr 2003, Chris Benham wrote:
> Forest,
> My answer to your question "Is there a simpler method that factors
> allof 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 .

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?  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.

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.

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.

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.
(Continue reading)

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Forest Simmons | 4 Apr 2003 01:59
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Re: Re: Strong Favourite Betrayal Criterion at last!

On Wed, 2 Apr 2003, Alex Small wrote  in part:

> 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.
>
> 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.
>

That's another good reason to restrict such methods to the Candidate Proxy
context or other applications where communication and coordination are
facilitated.

Forest

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Alex Small | 4 Apr 2003 07:22
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Re: Re: Strong FBC at last! ....Approval Runoff

Chris-

I don't quite follow the method that you describe.  Could you give me a
simple, step-by-step description of the method and its ballots?

Alex

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James Gilmour | 4 Apr 2003 09:05
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RE: IRV in action

Dave Ketchum  Sent: 02 April 2003 18:43
<Lots CUT by JG>
>  >>True IRV weakness that I see:
>  >>      44 candidates got some first place votes and can, possibly, win -
>  >>          even with two to get started with (candidates with only one
>  >>could list them next).
>  >>
I asked:
>  > I don't understand this comment.  What would the candidates list?
>  >
Dave replied:
> Let me try for better wording:  Assuming there was only one ballot listing
> candidate X first, this ballot's second choice could have been Y, one of
> the candidates that started with only 2 first choice votes.  This would
> mean Y now has 3 votes, and possibly can advance as other weak candidates
> are discarded and their votes reassigned.

Thanks.  I now understand completely.

>  >>      Some of the above may have got only one - here the IRV counters
>  >>decide which of these die now and which, if any, get a chance to advance.
>  >>
>  >
>  > What else can you do when you encounter a tie?  In the House of Lords
> by-election
>  > election, the Returning Officer would appear to have made the decision
> to exclude
>  > the tied candidates in alphabetical order.  Our regulations for public
> elections
>  > require the casting of lots to determine which of the tied candidates
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Gmane