IRV inconsistency

[DEMOREP1 at aol.com]

Mr. Simmons wrote in part-

As Richard says, IRV ignores and trashes valuable information willy nilly
and still pretends to come up with a top notch winner. All of IRV's
shortcomings can be traced back to this wasting of information.
---
D-
For newer folks (and a reminder for older folks) -- with 3 or more choices 
(or even 2 choices)-- there are Head to Head and place votes tables.

Head to Head Table (/ = ahead of)
       A     B     C
A     X    A/B  A/C
B    B/A   X     B/C
C    C/A   C/B    X

Place Votes Table
        1     2    3
A     A1  A2  A3
B     B1   B2  B3
C     C1   C2  C3

IRV only uses the 1st choice votes part of the Place Votes Table which is why 
it is so defective.

FFrom election-methods-list-request at eskimo.com  Wed May 16 03:18:30 2001
Received: (from smartlst at localhost)
	by mx1.eskimo.com (8.9.1a/8.8.8) id DAA01596;
	Wed, 16 May 2001 03:16:08 -0700
Resent-Date: Wed, 16 May 2001 03:16:08 -0700
Message-ID: <3B025326.A81537B1 at sol.physik.tu-berlin.de>
Date: Wed, 16 May 2001 12:15:02 +0200
From: Markus Schulze <schulze at sol.physik.tu-berlin.de>
X-Mailer: Mozilla 4.51 [de]C-CCK-MCD DT  (WinNT; I)
X-Accept-Language: de
MIME-Version: 1.0
To: election-methods-list at eskimo.com
Subject: Re: [EM] IRV inconsistency
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Resent-Message-ID: <"mH6Mb1.0.tO.eDb0x"@mx1>
Resent-From: election-methods-list at eskimo.com
Reply-To: election-methods-list at eskimo.com
X-Mailing-List: <election-methods-list at eskimo.com> archive/latest/6160
X-Loop: election-methods-list at eskimo.com
Precedence: list
Resent-Sender: election-methods-list-request at eskimo.com

Dear Richard,

you wrote (15 May 2001):
> Markus wrote (15 May 2001):
> > Richard wrote (14 May 2001):
> > > Another consequence of the summability failure is that reporting IRV
> > > results will be very complicated. At least for Condorcet you could
> > > publish the overall pairwise matrix (and also the pairwise matrices for
> > > individual counties or precincts or whatever the desired resolution is).
> >
> > I guess that IRV supporters will say that --for a voter to see what his
> > vote did-- it is sufficient to publish the votes of each IRV step.
>
> It may be sufficient for some, but I would think at least a few voters
> would demand more complete information about an election that will
> determine many aspects of their lives for the next several years.
> Exactly where do the numbers come from in each step? If there were
> 100000 A votes in the first round, and A got eliminated, how many were
> ABC votes and how many were ACB votes? This can be determined by the
> difference between first and second round votes for B and C. But how
> many of the B votes were BAC votes and how many of the C votes were
> CAB votes?

However, also the pairwise matrix doesn't say how many BAC votes there are.
You seem to believe that the voters want to know how many BAC votes there
are only when IRV is used but not when a pairwise method is used.

Markus Schulze

rom election-methods-list-request at eskimo.com  Wed May 16 03:18:30 2001
Received: (from smartlst at localhost)
	by mx1.eskimo.com (8.9.1a/8.8.8) id DAA01555;
	Wed, 16 May 2001 03:15:58 -0700
Resent-Date: Wed, 16 May 2001 03:15:58 -0700
Message-ID: <3B0252E8.3BE6190D at sol.physik.tu-berlin.de>
Date: Wed, 16 May 2001 12:14:02 +0200
From: Markus Schulze <schulze at sol.physik.tu-berlin.de>
X-Mailer: Mozilla 4.51 [de]C-CCK-MCD DT  (WinNT; I)
X-Accept-Language: de
MIME-Version: 1.0
To: election-methods-list at eskimo.com
Subject: Re: [EM] IRV inconsistency
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Resent-Message-ID: <"LmVdt2.0.EO.TDb0x"@mx1>
Resent-From: election-methods-list at eskimo.com
Reply-To: election-methods-list at eskimo.com
X-Mailing-List: <election-methods-list at eskimo.com> archive/latest/6159
X-Loop: election-methods-list at eskimo.com
Precedence: list
Resent-Sender: election-methods-list-request at eskimo.com

Dear Forest,

here is an example that shows that the Condorcet criterion
and the consistency criterion are incompatible.

   40 voters vote A > B > C.
   35 voters vote B > C > A.
   25 voters vote C > A > B.

Case 1: Suppose that candidate A is elected. Then when you add
51 A > C > B voters and 49 C > B > A voters, the winner is
changed to candidate C.

Case 2: Suppose that candidate B is elected. Then when you add
51 B > A > C voters and 49 A > C > B voters, the winner is
changed to candidate A.

Case 3: Suppose that candidate C is elected. Then when you add
51 C > B > A voters and 49 B > A > C voters, the winner is
changed to candidate B.

******

You wrote (15 May 2001):
> As Richard says, IRV ignores and trashes valuable information
> willy nilly and still pretends to come up with a top notch
> winner. All of IRV's shortcomings can be traced back to this
> wasting of information.

It is not feasible to say that the one election method uses
more information than the other. All election methods use the
same information. They only interpret it differently. Election
methods only differ in how important they consider which part
of this information.

******

You wrote (15 May 2001):
> This is analogous to the fact that Condorcet methods violate
> the Reverse Symmetry Criterion.

The Condorcet criterion and the Reverse Symmetry Criterion
are not incompatible. There are good Condorcet methods that
meet Reversal Symmetry. Please read Blake Cretney's website
(http://www.fortunecity.com/meltingpot/harrow/124).

Markus Schulze