[EM] RE: [Condorcet] Plain English description of Schulze(wv)

Simmons, Forest simmonfo at up.edu
Wed Sep 14 14:33:18 PDT 2005

The plain English description of Shulze is pretty good except for the last step (5), which is incorrect.  In Shulze you nullify the weakest defeat in a cycle.  The "in a cycle" part is extremely important.
To see this point suppose that after (properly) eliminating some weak defeats you get to the point where the remaining defeats are
X>Y>Z>X,  A>B>C>A, and X>A.  Suppose that the X>A defeat is the weakest of these.  To nullify it would wipe out the information that the winner should come from the XYZ cycle.


From: Condorcet at yahoogroups.com on behalf of John B. Hodges
Sent: Tue 9/13/2005 3:08 PM
To: Condorcet at yahoogroups.com
Subject: [Condorcet] Plain English description of Schulze(wv)

Jeff Fisher wrote:
>My attempt, slightly more formulaic: [for Schulze(wv) ]
>1.  Use voters' rankings to simulate an instant round-robin of
>head-to-head contests among all candidates in a race.
>2.  If one emerges undefeated, then that candidate is declared the
>winner. Otherwise...
>3.  Find the smallest set of candidates whose only defeats are to one another.
>4.  Sort the pairings within that set according to the number of
>votes on the winning side.
>5.  Discard/nullify/ignore the result of smallest winning vote and
>go back to #2.
>-- JRF [Jeff Fisher]

(JBH) BRAVO! This is the first description of the Schulze method that
I've seen, that the averge voter might finish reading.

My concern has been whether the tie-breaking (cycle-breaking) method
had intuitive appeal, whether the winner of a tie-breaker could make
a plausible claim to being the legitimate "people's choice". The
above description is clear enough, that the claim is weak but about
as good as one might expect, given that the election is basically a

There are many other tie-breakers that might be imagined. Some, like
having a plurality of first-rank votes, are simpler than the above.
This is where the technical analysis and long vetting of the Schulze
method may carry weight with the voters- not in persuading them to
consider or adopt the method, but to dissuade them from tinkering
with it. We can say, "Lots of people have already done that, it's
surprisingly hard to find a tie-breaker that does not have unwanted
side-effects. This one has been found to do the job relatively
John B. Hodges, jbhodges@  @usit.net
Do Justice, Love Mercy, and Be Irreverent.

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