Consensus on IRV & Runoff?

MIKE OSSIPOFF nkklrp at hotmail.com
Wed Jan 30 00:29:08 PST 2002

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Do we have a consensus that the instant runoff vote (IRV) is MATHEMATICALLY
better than the common two step plurality vote (primary) with a follow-up
runoff between the 2 top plurality vote getters? It seems to me that it
cannot
be worse, given that manipulation is bad. As far as I can see, the only
mathematically provable difference between them is that IRV is less
manipulatable. They share the same faults, including non-monotonicity. With
3
candidates, I believe they are mathematically identical.

Here's a big difference:

With Runoff, if the sincere CW comes in 1st or 2nd as indicated
favorite in the primary, s/he can't lose.

With IRV, it doesn't matter if the sincere CW is the expressed
favorite of more people than any other candidate--s/he can still
be eliminated & lose.

Another difference:

For Runoff, the mathematical strategy isn't too complicated to
write in one line. Cox, in one of his books, describes Runoff's
mathematical strategy for maximizing utility expectation.

It only involves a few summations, maybe 3 or 5.

IRV strategy would be horrendously more complicated. If IRV were
it wouldn't matter to me, since I'd boycott the elections anyway,
and urge others to.

Mike Ossipoff

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