Reply on EM to Mike's Reply on ER
landerso at ida.org
Wed Apr 3 07:48:50 PST 1996
Mike Ossipoff posted two messages replying to me, on ER, on April 1--one at
16:17 PST and one at 18:12 PST. I disagree in one way or another with
essentially everything in the 16:17 message, and I disagree with much, but not
everything, in the 18:12 message. One of the things that I agree with in that
latter message is:
On Apr 1, 6:12pm, Mike Ossipoff wrote:
> Subject: [ER] Re: Reply to Bruce Anderson
> Sorry if this is off the topic of this list,
which is why I am posting this response on EM.
Rather than attempt to respond to everything, or to those points that we are
least likely to reach agreement upon, I think that it might be more productive
to respond to the points on which we are most likely to be able to reach some
type of agreement.
> I just wanted to give credit to Bruce where it's due, though I
> don't agree with him that Smith-Condorcet is too complicated to
> propose to the public, or that Copeland's method can be considered
> as good as plain Condorcet or Smith-Condorcet, when it comes
> to the standards that are the reason why we electoral reformers
> want a better single-winner method.
I don't think I ever said that (in my notation) Smith//Condorcet is too
complicated to propose to the public. I said that it is significantly more
complicated than just Condorcet. I also said that it is significantly better
than just Condorcet. I also said that I thought that there are still other
voting methods that are both better and simpler than Smith//Condorcet. None of
these statements mean that Smith//Condorcet is too complicated for public use.
In fact, I think that it is too simple, and that the public could accept the
slightly more complex method I denote by Smith//Condorcet//Plurality. I presume
that Mike thinks that Smith//Condorcet is slightly more complicated and slightly
better than just Condorcet. Maybe we'll never reach agreement on "slightly"
versus "significantly," but maybe we can agree on the unmodified "more."
Determining which standards are most desirable would be a good topic to
debate--too good to try to rush out in a "quick-and-dirty" e-mail posting.
As an aside, in my notation X-Y either means a particular voting method jointly
proposed by X and Y, or it means a particular voting method where X and Y alone
have no intrinsic meaning. X//Y means that X and Y are both ranked-ballot
single-winner voting methods where, if X produces a single winner, then that
winner is the X//Y winner; while if X results in tied winners, then the result
of applying method Y to this set of tied winners yields the overall X//Y
> When I said that any method having the no-show paradox must also
> be non-monotonic according to the official academic definition, when
> the number of voters doesn't change, I believed it at the time. Maybe
> it's true, but my reason for believing that when I said it wasn't
> correct. It doesn't matter though, since we were talking about a
> particular method, Instant Runoff, which, as I said, is known to
> be nonmonotonic anyway,
Let's say that a ranked-ballot method that cannot exhibit the no-show paradox is
"turnout-monotonic" and that a ranked-ballot method that satisfies the standard
definition of monotonic is also called "preference-monotonic." Then I can't
prove that a turnout-monotonic method is necessarily preference-monotonic, nor
can I prove that a preference-monotonic method is necessarily turnout-monotonic.
Indeed, I suspect that sufficiently weird voting methods can be constructed
showing that either one can be satisfied without satisfying the other. However,
I also suspect that the typically discussed voting methods either satisfy both
or fail both. More specifically here, the issue of whether either type of
monotonicity implies the other was clearly what I was talking about in my
response to Rob's message which, in turn, Mike was responding to--I certainly
was not just "talking about a particular method, Instant Runoff, which ... is
known to be nonmonotonic anyway".
In fact, I have never used and I strongly oppose the use of the term "Instant
Runoff" to mean MPV/STV/Hare voting. Runoff has an established meaning, at
least it does in the United States--it's the pairwise match between the top two
plurality leaders, if neither has a strict majority. So an "instant runoff"
should be that pairwise match based on the voters ranked ballots. I suggest
calling the single-winner version of STV/Hare by the abbreviation "PEV."
Supporters could say PEV stands for Preferentially Empowered Voting, while
others could say that PEV stands for Plurality Elimination Voting, which is what
it really is.
In my opinion, what Rob was trying to discuss in his original message, and what
Mike keeps repeating--that PEV fails (in the terminology just above) BOTH
preference-monotonicity AND turnout-monotonicity--is crucially important. I
think these failures, taken together, form the single greatest flaw of PEV.
Perhaps that's why I was somewhat upset when Rob presented this flaw the way he
did. I urge Rob, and Mike, and anyone else interested, to develop powerfully
worded but technically correct presentations to show why PEV, and all other
voting methods with this flaw, are quite undesirable.
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