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Re: [EM] Beatpath question

RL
Rob LeGrand
Mon, Oct 5, 2015 9:15 PM

Jameson wrote:

I can show (under reasonable strategic assumptions) that my delegated
system SODA elects one of the candidates who beats all with a winning vote
beatpath of length 2 or less, if there is any such candidate. "A beats B
with a winning vote beatpath of length 2" means: there is some C such that
the minimium of (votes for A against C, votes for C against B) is greater
than votes for B against A.
Obviously, if we allow any length of beatpath, and if there are no ties,
there must be some beats-all winner. But is it possible that there is no
winner with beatpaths of length 2 or less? Can anybody give an example of
such an electorate?

If I understand you correctly, this electorate does what you want:

29:A>C>B>D
15:B>D>A>C
16:D>C>B>A

If beatpaths of all lengths are considered, as in the Schulze method, A
loses no beatpath comparisons.  In particular, the beatpath A>C>B>D is
stronger than D>A.  But A needs a beatpath that long to defeat D; the
beatpaths A>B>D and A>C>D are weaker than D>A.  Using only beatpaths of
length 2 or less, every candidate loses a beatpath comparison.

What would strategic SODA do in the above case?

--
Rob LeGrand
rob@approvalvoting.org

Jameson wrote: > I can show (under reasonable strategic assumptions) that my delegated > system SODA elects one of the candidates who beats all with a winning vote > beatpath of length 2 or less, if there is any such candidate. "A beats B > with a winning vote beatpath of length 2" means: there is some C such that > the minimium of (votes for A against C, votes for C against B) is greater > than votes for B against A. > Obviously, if we allow any length of beatpath, and if there are no ties, > there must be some beats-all winner. But is it possible that there is no > winner with beatpaths of length 2 or less? Can anybody give an example of > such an electorate? If I understand you correctly, this electorate does what you want: 29:A>C>B>D 15:B>D>A>C 16:D>C>B>A If beatpaths of all lengths are considered, as in the Schulze method, A loses no beatpath comparisons. In particular, the beatpath A>C>B>D is stronger than D>A. But A needs a beatpath that long to defeat D; the beatpaths A>B>D and A>C>D are weaker than D>A. Using only beatpaths of length 2 or less, every candidate loses a beatpath comparison. What would strategic SODA do in the above case? -- Rob LeGrand rob@approvalvoting.org