[EM] Why I Prefer IRV to Condorcet

[Markus Schulze]

Hallo,

Juho Laatu wrote (28 Nov 2008):

> I didn't quite get this. When evaluating
> candidate X minmax just checks if voters
> would be interested in changing X to some
> other candidate (in one step), while
> methods like Schulze and Ranked Pairs may
> base their evaluation on chains of victories
> leading to X.

Suppose the MinMax score of a set Y of candidates
is the strength of the strongest win of
a candidate A outside the set Y against
a candidate B inside the set Y. Then the
Schulze method (but not the Ranked Pairs
method) guarantees that the winner is
always chosen from the set with minimum
MinMax score. See section 9 of my paper:

http://m-schulze.webhop.net/schulze1.pdf

Because of this reason, the worst pairwise
defeat of the Schulze winner is usually very
weak. And, in most cases, the Schulze winner
is identical to the MinMax winner. This has
been confirmed by Norman Petry and Jobst
Heitzig (with different models):

http://lists.electorama.com/pipermail/election-methods-electorama.com/2000-November/004540.html
http://lists.electorama.com/pipermail/election-methods-electorama.com/2004-May/012801.html

Markus Schulze