[EM] The truth about Instant Runoff Voting

James Green-Armytage jarmyta at antioch-college.edu
Thu May 19 16:45:48 PDT 2005

Ralph Suter, you wrote:
"The truth about Instant Runoff Voting"
	Rob Lanphier subsequently linked the page to electorama.com. I think that
it would be a better critique of IRV with some revision, as indicated

>The big problem with IRV is that the winner is very often a
>candidate who would have lost to one or more of the other
>candidates in a one to one contest. This is not just an
>occasional problem but would likely happen frequently.
>The big problem with IRR is that sometimes there is no
>candidate who will defeat each of the others. In such
>cases, no matter which candidate is declared the winner,
>there would be at least one other candidate who would
>defeat the declared winner in a one to one contest.

	I think that it is very misleading to say that this is "the big problem
with IRR." More accurately, it is the big problem with single winner
voting in general. 
	If I had to name any one thing as "the problem with IRR," I would
probably say vulnerability to burying, but I don't necessarily recommend
that you put this in your article.
>No one can say for sure how often these problems would
>occur in actual elections run with either IRV or IRR. My
>guess is that a non-majority IRR winner would be much rarer
>than a non-majority IRV winner.

Actually, I think that we can say for sure that a non-majority IRV winner
would occur more frequently than a non-majority IRR winner, as you seem to
define them, assuming sincere votes. 
Non-majority IRV winner: An IRV winner X such that at least one candidate
pairwise beats X.
Non-majority IRR winner: An IRR winner Y such that at least one candidate
pairwise beats Y.
(Are these definitions what you intended?)

Case 1: There is a majority rule cycle with respect to expressed
preferences. Any IRV winner is a non-majority IRV winner. Any IRR winner
is a non-majority IRR winner.
Case 2: There is a Condorcet winner with respect to expressed preferences.
The IRV winner may or may not be a non-majority IRV winner. The IRR winner
is certainly not a non-majority IRR winner.
Conclusion: By my understanding of your definitions, non-majority IRV
winners necessarily occur with greater frequency than non-majority IRR

James Green-Armytage

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