[EM] equal rankings IRV

[Markus Schulze]

Dear Chris Benham,

you wrote (15 June 2004):
> Judging by the example at Steve Eppley's site, it seems
> to meet his (similar) "Non-Drastic Defense" criterion.

This is Steve Eppley's "Non-Drastic Defense" criterion:
> Non-Drastic Defense:  Each voter must be allowed to vote
> as many alternatives tied for top as she wishes, and for
> all x e A, x must not be elected if there exists y e A
> such that that more than half of the voters vote y over x
> and no worse than tied for top.

Here is an example where ER-IRV(fractional) violates
Steve Eppley's "Non-Drastic Defense" criterion:

   20 A=B=C>E>...
   20 A=B=D>E>...
   20 A=C=D>E>...

   7 B>E>...
   7 C>E>...
   7 D>E>...

   38 E>...

   A majority of the voters strictly prefers candidate A
   to candidate E and ranks candidate A tied for top.
   Nevertheless, candidate E is the winner.

Markus Schulze