Kevin and Chris, You’re both right, my “proof” only showed that raising the winner W could not hurt her prospects on ballots where she was already approved or on ballots where she was rated at the highest currently unapproved level. But , as Kevin pointed out, if there were candidates at two or more levels above W, and not all of these levels were above the current cutoff, the cut off could lower without lowering all of the way down to W.
Back to the drawing board. I’m starting to think that it may be impossible to have any kind of monotonic, non-trivial DSV method for automatically choosing approval cutoffs. Forest ---- Election-Methods mailing list - see http://electorama.com/em for list info
