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David Gamble wrote:<br><br>
<blockquote type=cite class=cite cite><font size=2>Monotonicity is
undoubtedly a desirable feature of an electoral method. I do however feel
that no method can be perfect and that other features are more important
( proportional representation of parties, proportional representation of
opinion, </font></blockquote><br>
I'm re-stating others here, but anyway...<br><br>
I'd agree that proportionality in parties or opinion is more important
than whether or not there is a bizarre result here or there. But
this is meaningless when considering a single winner, where there is no
"proportionality" to be had. In that case, you just want
the candidate that best represents everyone in the district. (That
may constitute a sort of "degenerate case" of proportionality,
I suppose.)<br><br>
<blockquote type=cite class=cite cite><font size=2>[and] maximum freedom
of voter choice regarding the individuals who represent you,
etc).</font></blockquote><br>
Does a voting system that has been shown to support a two-party duopoly
really provide this? We can debate until the cows come home about
how much choice approval/Concorcet/etc. will provide, but from what I can
see there's no reason to be satisfied with IRV in that regard.<br><br>
<blockquote type=cite class=cite cite><font size=2>As to the
non-monotonicity of IRV and STV let me give an alternative definition of
non-monotonicity <br><br>
" Non-monotonicity -something that occurs more frequently in
theoretical examples than real elections "</font></blockquote><br>
This is true, since monotonicity violations can only really occur when
there are more than two viable candidates. While this is a
desirable situation (because it increases voter choice) but it is
vanishingly rare in places where IRV is used.<br><br>
That said, the lack of frequent monotonicity violations doesn't get IRV
off the hook in my mind. The fact that a method violates
monotonicity means that it is strongly vulnerable to strategic
manipulation. Sure enough, IRV has all sorts of situations where it
makes sense to move your compromise up on the ballot, and it can be
extremely hard for the voter to figure out when to do this and when not
to.<br><br>
I consider monotonicity one of the two most important
"academic" criteria, among those that are violated by any
reasonable methods. The other one is idependence from clones.
Clone-independence means that the election can effectively merge multiple
candidates that always appear next to each other on the ballot.
Adding or removing a candidate that always appears just after a given
candidate on every ballot will not change the result.<br><br>
If a method fails clone-independence, then it will either have a bad
"spoiler" problem (like plurality does), or will have the
bizarre effect of making parties want to run as many candidates as
possible (like Borda does). IRV actually passes clone-independence,
which is one point in its favor.<br><br>
Again, like monotonicity, it's not the failure of the precise definition
of clone-independence that I have a problem with. It's that failing
to satisfy that criteria is a red flag that other problems
exist.<br><br>
As a side note, only a few methods discussed here actually pass both
clone-independence AND monotonicity. Beatpath, ranked pairs,
approval, cardinal rankings, median ranking, and extended MCA (Bucklin
with equal rankings allowed) all satisfy both. These are the only
methods I know of that I'd work to get adopted for single-winner
reform.<br><br>
-Adam</html>