[Election-Methods] Why monotonicity? (was: Smith + mono-add-top?)

daniel radetsky dradetsky at gmail.com
Wed Jan 9 19:09:03 PST 2008

On Jan 1, 2008 1:15 PM, Steve Eppley <SEppley at alumni.caltech.edu> wrote:

> Are monotonic methods less manipulable than non-monotonic methods?  I've
> never heard any evidence of that.

I'm going to assume that you are not asking something like "For all possible
voting methods and some reasonable manipulability metric, is the average
manipulability of the monotonic methods lower than the average
manipulability of the non-monotonic methods?" For if a method is
non-monotonic, this means that there is a way to manipulate it. If you are
asking whether given the choice between (say) a monotonic,
non-clone-independent method and a non-monotonic, clone-independent method,
all else being equal, then perhaps as you suggest, clone-independence is
more important. However, I was under the impression that one of the goals of
studying voting methods was to avoid having to make this choice.

In any case, resistance to manipulability is not the only reason to desire a
particular property for a voting system. Another important quality is
transparency: does casting a vote do what the voter thinks it does? A voter
thinks that when he increases his vote for X (whatever "increases" means in
the system in question), he is helping X win. In a non-monotonic system,
he's wrong, or at least not guaranteed to be right. This is bad. Right?

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