Instant Runoff Voting: take another look

[David Farber <dave () farber net>]

Begin forwarded message:

From: Stephen Unger <unger () cs columbia edu>
Date: March 26, 2007 11:10:16 AM EDT
To: Farber list <dave () farber net>
Subject: Instant Runoff Voting: take another look

In an effort to do something about the third party "spoiler" effect,
which has severely hampered the growth of parties ranging from the
Green Party to the Libertarian Party, many thoughtful people have been
promoting the instant runoff voting (IRV) idea. In this method of
voting, each voter ranks all of the candidates. If nobody wins a
majority of the first-place votes, the second-place votes on ballots
listing that candidate in first place are counted. This process is
iterated until some candidate has a majority.

This scheme has the merit of encouraging people to vote for third
party candidates with little chance of winning, since, when those
candidates are eliminated, the second-place votes can be used to help
choose the winner among the front runners. So, the argument goes,
voters for third parties don't have to feel that their votes are
wasted.

However, while IRV does work as advertised in some important
situations, there are also situations in which it produces bizarre
results. For example, there are cases where a vote FOR X can help
DEFEAT X. Another problem with IRV is that counting of votes cannot be
decentralized. All ballots for a statewide election, for example, must
be processed together. This is in contrast to the distributed counting
process (precinct by precinct) used conventionally for other
methods. This increases costs and makes it more difficult to safeguard
against error or fraud.

Both range voting and approval voting also eliminate the spoiler
effect, and neither suffers from the problems inherent in IRV. An
article comparing IRV with range and approval voting is at

http://www1.cs.columbia.edu/~unger/myBlog/endsandmeansblog.html

Steve
............

Stephen H. Unger


Stephen H. Unger
Professor
Computer Science Department
Columbia University
............


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