[EM] Better answer to WS's example
Michael Ossipoff
mikeo2106 at msn.com
Thu Jul 19 07:14:30 PDT 2007
WS--
Let me word my answer better, now that I've had a more thorough look at the
example.
Your objection was that if the Blues order-reverse against Red, and if the
Reds do defensive truncation, that will elect Hitler. In my most recent
posting, I correctly pointed out that Hitler doesn't win then. I'll get to
that again, but disregard it for now.
Effectively, your claim, that offensive order-reversal countered by
defensive truncation will elect Hitler in the example, is correct for wv
Condorcet, and I'll tell why in a minute. The claim is literally true for
MDDA and MAMPO. By the way, I was incorrect when I said that MAMPO elects
Hitler when both the Reds and Blues truncate against eachother. WV, MDDA and
MAMPO all return an R, B tie then.
But that's a good thing. It means that when the Reds announce that they're
going to truncate, or when numerous articles, ads and letters to the editor,
etc. advise them to, then the Blues would be very foolish to order-reverse.
In fact I claim that it isn't a problem at all. If the Blues vote that they
like Hitler better than Red, doing so even after someone has told them what
the result will be, then they shouldn't be surprised if they get Hitler. It
won't happen. There may be two nuttys, but the electorate isn't 51% nuttys.
What about the fact that, strictly speaking, with the numbers exactly as you
wrote them, Hitler doesen't win? If it were likely for Hitler to lose then,
the Reds would have no threat or deterrence against the offensive
order-reversal. But it only happens if Red and Blue are really in a pairwise
tie. Pairwise ties are vanishingly rare in public elections. If Red has even
one more vote than Blue, then Hitler wins, when the Blues order-reverse and
the Reds defensively truncate.
If Blue is bigger than Red, then the Blues don't need strategy to win. Only
if there's a pairwise tie between Red and Blue do the Blues gain by the
offensive order-reversal. And, if Blue and Red look about equal, then of
course it's many times more likely that Red pair-beats Blue than that Red
and Blue are in an exact pairwise tie. Therefore, offensive order-reversal
by the Blues would be a big mistake.
So that's my answer. The example won't happen, because the Blues will be
deterred, with MDDA, MAMPO, and with wv Condorcet.
The Reds, when announcing their truncation, could invite the Blues to do the
same. With any of the 3 abovementioned rank methods, the result will be a
Blue-Red tie.
With MDDA and MAMPO, the Reds would also want to truncate if they felt that
the Blues might do so.
Mike Ossipoff
More information about the Election-Methods
mailing list