[EM] Paper by Ron Rivest

[Andy Jennings]

> here is an interesting paper by Ron Rivest:
>
> http://people.csail.mit.edu/rivest/RivestShen-AnOptimalSingleWinnerPreferentialVotingSystemBasedOnGameTheory.pdf


Very interesting paper.  It contains a very good rationale for using a
random election method (when there is a Condorcet cycle).

The GT method in the paper is intriguing.  It meets the Condorcet
criterion, but if there is a Condorcet cycle then it does not
necessarily meet the Pareto criterion!  As the paper says, one of the
defeats in the Condorcet cycle could be unanimous but the GT method
would probably assign all candidates in the cycle a positive
probability of winning.  (Though the paper claims this can be done
with a 3-cycle, it seems to me that you would need at least a
4-cycle.)

Is anyone willing to reconsider the Pareto criterion in the case of a
Condorcet cycle?  I don't know if I am, but it's worth thinking about.

Andy Jennings