CSSE = Simmons' Method ?

Forest Simmons fsimmons at pcc.edu
Thu Feb 14 16:33:31 PST 2002


The more I think about it the more I prefer Borda Seeded Bubble Sort as a
simple, high utility, hard to manipulate, method satisfying the Condorcet
Criterion, when limited to pure ranked preference ballots where
truncation, Yes/No, NOTB, etc. are not allowed or provided for. 

The Borda order is sorted down to the bottom seeded candidate Z by
(recursively) bubble sorting all of the candidates above candidate Z
before percolating Z upward until Z is defeated in a pairwise comparison.

This method is easy to describe (even without the simplicity of
recursion), always picks a winner from the Smith set, is monotonic (I
believe), satisfies the Reverse Symmetry Criterion, and encourages
insincere ranking of candidates even less than Borda Seeded Single
elimination. 

In a nut shell here's why I think it gives less incentive for insincere
ranking:

Suppose you prefer X to Y but you are told that X might spoil Y's chance
of winning without X going on to victory (because Y has a better chance
according to the polls). 

In both methods (Bubble and Single Elimination) you could say, "To heck
with the polls, if X gets a higher Borda count than Y, then I say X has a
better chance.  I don't trust those polls anyway." 

But after you vote X ahead of Y you begin to worry.  What if X is seeded
below Y, and then (in single elimination) over-takes and defeats Y, and
then goes no further, dashing Y's hopes of winning without having the
steam to keep going?

This could never happen in Bubble Sort.  If X is seeded below Y, then Y
has already risen to its apogee before any possible challenge from X. 
Candidate X cannot hurt Y from below in Bubble Sort.

The Borda Seeding should give the method near maximal Social Utility for a
method based on pure ranked preference ballots (no Approval marker, etc.)
and satisfying the condition of always picking from the Smith set. 

Forest





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