[EM] IRV vs BC

Steve Barney BARNES99 at vaxa.cis.uwosh.edu
Sun Mar 11 13:26:14 PST 2001


It seems to me that there is a glaring weakness in arguments that the 
Borda Count (BC) is inferior, overall, to the Instant Runoff Vote 
(IRV) because it is more manipulatable, even if it is more 

First of all, it is worth noting that it has been mathematically 
proven that all voting procedure necessarily must be manipulatable 
(M. Satterthwaite, "Strategy-proofness and Arrow's conditions," 
_Journal of Economic Theory_, 1975, 10: 187-217). Therefore, since 
manipulatability is only a matter of degree, the most you can claim 
is that the BC is more manipulatable than, for example, the IRV.

Anyway, lets take it for granted that the BC is relatively vulnerable 
to successful manipulation by strategic or insincere voting, in 
comparison to the IRV; that is to say, that the BC can elect someone 
other than the voters' truly most preferred candidate, to the benefit 
of voters who strategically submit dishonest or insincere votes.

Well, what about the argument that the BC has been mathematically 
proven (see Donald Saari, "Mathematical Structure of Voting 
Paradoxes," _Journal of Economic Theory_, January 2000, pgs 1-102; or 
Donald Saari, "The Symmetry and Complexity of Elections," 
<http-//www.math.nwu.edu/~d_saari/vote/expos.pdf>) to be the ONLY 
method which can be guaranteed to always accurately reflect the 
voters' preferences when they vote honestly and sincerely? That is, 
what about Saari's mathematical proof that the BC is the only method 
which always gives an accurate accounting of THE VOTES THEMSELVES, 
regardless of whether those votes are honest and sincere or not? 
Shouldn't that count for something? (For the sake of argument, let's 
take Saari's analysis for granted, and assume that it is true that 
the BC is indeed the best method for determining the most preferred 
candidate from SINCERE votes.) Given the soundness of Saari's 
analysis, couldn't the accuracy of the BC outweigh its 
manipulatability, in comparison to the IRV?

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