[EM] Margin Schulze method

Robert Verron robert.verron at mail.com
Fri Apr 30 12:08:59 PDT 2021


In the Schulze method, the strength of a path is defined in terms of an
absolute number of voters. Specifically, if we consider a link between A
and B (that is, a direct path from A to B) and write d[A, B] for the
number of voters strictly preferring A to B (and d[B, A] in a similar
way), why is the strength of the link defined as max(d[A, B], d[B, A]) ?
(I'll call this the "max version")

Schulze [1] allows several definitions of the strength of a link,
including the margin. That is, the strength of a link between A and B
could be |d[A, B] - d[B, A]| (the "margin version").

I've also noticed that, unlike the max version, the margin version
satisfies the chicken dilemma criterion.

So, I don't know why the max version was picked. Is there an actual
reason ? Could someone please explain or link to a
discussion/paper/whatever about it ?

Thanks !

Robert Verron.

[1] Schulze, M. A new monotonic, clone-independent, reversal symmetric,
and condorcet-consistent single-winner election method. Soc Choice Welf
36, 267–303 (2011). https://doi.org/10.1007/s00355-010-0475-4

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