[EM] Burlington VT reconsidering IRV 10 years after IRV failed to elect the Condorcet Winner

Markus Schulze markus.schulze8 at gmail.com
Sun Dec 8 08:24:25 PST 2019


Toby Pereira wrote:

 > I know I'm going a bit off-topic, but what
 > is the estimated probability that Schulze and
 > Ranked Pairs would give a different result in
 > a real-life election? I'd be surprised if it
 > was more than about 1 in 10,000, and where
 > there was a different winner between them,
 > neither winner would be so much obviously the
 > "right" winner that it would cause protests
 > in the streets if the other one were to win.

The Schulze winner is almost always identical
to the MinMax winner, while the Tideman winner
differs from the MinMax winner needlessly

Norman Petry's calculations:

Jobst Heitzig's calculations:

Barry Wright's calculations (section 8):

This means that, in those cases where the
Schulze winner differs from the Tideman winner,
the worst pairwise defeat of the Tideman winner
usually is worse than the worst pairwise defeat
of the Schulze winner. In my opinion, this is
an advantage for the Schulze method because the
worse the worst pairwise defeat of the winner
is the more difficult it is to justify the
election result without having to go into
the details of the counting process.

I also believe that the fact, that the
MinMax method satisfies mono-add-top and
mono-remove-bottom, and the fact, that the
Schulze winner is almost always identical to
the MinMax winner, together mean that the
Schulze method violates mono-add-top or
mono-remove-bottom less frequently than
the Tideman method.

Markus Schulze

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