[EM] Cloneproof Schwartz Sequential Dropping / Schulze

[James Green-Armytage]

On July 18th, Markus Schulze wrote:
>Dear James Green-Armytage,
>
>Example:
>
>   A:B=50:50
>   A:C=50:50
>   A:D=50:50
>   B:C=75:25
>   B:D=40:60
>   C:D=65:35
>
>SSD would declare A the winner since he is the only candidate
>who isn't beaten by anybody.
>
>CSSD would drop B:D to get rid of the B>C>D>B cycle.
>And then it would report a tie between A and B.
>
>You can also find an old description of CSSD here:
>http://groups.yahoo.com/group/election-methods-list/message/2291
>
>Markus Schulze

I reply:

Dear Markus Schulze,

Thank you very much for the example. It certainly helped to show how SSD
and CSSD can produce different results. The one thing that I don't seem to
understand yet, though, is what makes CSSD cloneproof where SSD is not. In
the example above, I don't think that there are any clones. Do you by any
chance know of an example where the addition of clones changes the result
in SSD but does not change the result in CSSD? I would be very much
obliged.

my best,
James Green-Armytage