I started this thread to compare IRV vs Condorcet, believing that IRV is
provably less capable and deserves discarding.
To make room to concentrate on this I call for a truce between Condorcet
and Range, though ready to claim that Condorcet meets voter needs better
than Range.
Approval is a side issue, though anything expressible there is also
expressible, easily, in Condorcet.
DWK
On Thu, 9 Oct 2008 16:37:05 -0400 (EDT) Stephen Unger wrote:
Steve
............
Stephen H. Unger
Professor (retired)
Computer Science Department
Columbia University
............
On Wed, 8 Oct 2008, Dave Ketchum wrote:
I suggest a two-step resolution:
Agree to a truce between Condorcet and Range, while they dispose of
IRV as being less capable than Condorcet.
Then go back to the war between Condorcet and Range.
Condorcet uses essentially the same ballot as IRV, with essentially the
same meaning:
Any IRV ballot would be acceptable to Condorcet.
Condorcet also accepts such as A=B.
IRV often demands that voters vote for more than one candidate;
Condorcet accepts as few or many as the voter offers.
IRV gives extra credit for ranking a candidate first, while Condorcet cares
only which is most liked. The following example shows this:
IRV starts by discarding B for least first-place votes, and then
solves A vs C.
Condorcet sees that B is liked better than A and B better than C, so
B wins.
Condorcet is better for validation:
All that is said by a collection of Condorcet voters, such as a
precinct, can be recorded in an NxN array. These arrays can be summed for
whole counties, states, etc.
When the first name on an IRV ballot loses, such as B in the example,
the next name on that ballot must be known and substituted.
An example:
42: C>B
39: A>B
10: B>A
4: B
5: B>C
B is the Condorcet winner, and also the first loser discarded by IRV.
Actually, IRV and Condorcet usually agree as to winner:
If most ballots agree as to top rank, that candidate wins.
Ditto agreement on most other ballots.
If there is a near tie among three or more, they often disagree but
usually get one of the leaders - matters little since the leaders were
about equally deserving.
IRV discarding the truly best liked, as in the example, is a strong
argument for discarding IRV.
*****
Good arguments for Condorcet over IRV.
*******
My 2-cents as to Condorcet vs Range:
Consider A good, B soso, and C bad:
In Condorcet I rank A>B>C, expressing my basic opinion.
In Range I rate A high and C low. Then I have a headache as to B -
the higher I rate B, the more danger of B beating A; the lower I rate B,
the more danger of C beating B.
********
Good point, but I think we need to look closer.
The basic weakness of Condorcet (or any other ranking scheme) compared
with range is that the vote A>B>C could mean "I think A is fine, B is
almost as good, and C is terrible" OR it could mean "I think A is
fine, B is very bad, and C is even worse". OR it could mean anything
in between. There is NO way for a voter to cast different votes that
distinguish among these cases.
In one sense a Condorcet weakness. In another sense Range has a weakness
of demanding that voters successfully understand and productively use Range
ratings.
This has the interesting consequence that the Condorcet voter is never
in a quandary in such a situation. The vote A>B>C is the best that can
be done to support A against all other candidates, and, at the same
time it does the best job of supporting B over C.
But the Range voter DOES have a problem when the polls indicate that
A, B, and C each have a chance to win. After giving A the maximum
score and C the minimum score, the problem for the voter who ranks
the candidates A>B>C is that giving B anything but the minimum score
might help B beat A, while giving B anything but the maximum score
might help C beat B, which would be bad if A's score is lower than
both the B- and C-scores. If most of the voters consider B to be
roughly midway between A and C in acceptability, then it is tough to
decide how to score B. But this might be considered as a real problem
having to do with the relative merits (in the eyes of voters) of the
candidates. It is not a problem for Condorcet voters simply because
their options are more restricted.
On the other hand, an RV election can produce a winner that is more
satisfying overall. Consider the following example, where X>>Y
indicates a very strong preference of X over Y.
4 A>>B>C
3 C>>B>A
2 B>A>C
1 B>C>A
In a Condorcet election, B would win (beats A 6-4 and C 7-3).
But, in an RV election (range 0-5), a plausible vote expressing the
same views would be:
A B C
4 5 1 0
3 0 1 5
2 3 5 0
1 0 5 3
The winner here is A (26-22-18). And this makes more sense, since 70%
of the voters think B is very bad.
For the same voter views, an Approval Voting election would almost
certainly also lead to A winning.
**********
Steve
.......>
--
[EMAIL PROTECTED] people.clarityconnect.com/webpages3/davek
Dave Ketchum 108 Halstead Ave, Owego, NY 13827-1708 607-687-5026
Do to no one what you would not want done to you.
If you want peace, work for justice.
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