IRO fails plurality CWs too.

Mike Ositoff ntk at
Sun Oct 11 19:40:03 PDT 1998


Before I get to the example, let me mention that IRO's proponents
often say that it gets rid of the lesser-of-2-evils problem. They're
talking about a particular special situation, like:

 47  45  8
  A   B  C
  B      B

The more extreme candidates are smaller--candidate size tapers
toward the extremes. But the extreme candidate is still big enough
to tip the scales between the more middle candidates when its votes
transfer inward.

Ok, then let's keep those assumptions, but say that there are
more candidates. For example:

 60 70 100 83 75
  A  B   C  D  E
  B            D

(I've only listed the 2nd choices that affect the result. Only
the extremes need get eliminated to establish C as a loser.

Note that in this example not only does IRO dump a CW, but
it dumps a  CW who has a plurality. So much for IRO advocates'
favoriteness standard.

And that isn't a rare special example. Though the middle candidate
of 3 will sometimes be the smallest, a voter distribution that
gives tapering support toward the extremes is especially plausible
& likely and in keeping with a normal distribution of voters
on the political spectrum.

So IRO not only fails the Condorcet Criterion & Monotonicity,
but it also fails the main standard that its proponents defend
it with: favoriteness.


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