[EM] Issues, Condorcet, and IRV (was: IRV vs. plurality)

[Markus Schulze]

Dear Eric,

Dave Ketchum wrote (9 Aug 2003):
> The example was presented by Markus Schulze, designed to
> give the results I described, when counting via BEAT PATH
> method.  Clearly you must have used a different method to
> get your different results. I do not like declaring a tie,
> for we prefer declaring a winner without tossing a coin
> when at all possible.

You wrote (9 Aug 2003):
> Yes, as I clearly stated, I was using my site and obviously
> not using either Beatpath or Basic Condorcet - that left
> only one option. This example clearly shows the flaw in the
> Beatpath Winner method. However, in a better RP method, the
> flaw disappears and a tie is declared.

Here is a concrete example where Tideman's ranked pairs method
violates the Participation criterion in a very drastic manner.

Situation 1:

   03 ACBED
   12 ACEBD
   07 BADCE
   02 CEBDA
   03 DABCE
   09 DCBEA
   01 DEBAC
   05 EACBD
   10 EBDAC
   01 ECBDA
   03 EDCAB
   04 EDCBA

   A:B=26:34
   A:C=41:19
   A:D=27:33
   A:E=25:35
   B:C=21:39
   B:D=40:20
   B:E=22:38
   C:D=23:37
   C:E=36:24
   D:E=20:40

   The ranked pairs winner is A.

Situation 2:

   3 ADBCE voters are added.

   A:B=29:34
   A:C=44:19
   A:D=30:33
   A:E=28:35
   B:C=24:39
   B:D=40:23
   B:E=25:38
   C:D=23:40
   C:E=39:24
   D:E=23:40

   Now, the ranked pairs winner is E.

Markus Schulze