[EM] Re: Nanson and Borda

[Rob LeGrand]

Kevin Venzke wrote:
> Do you know why it would be, that you obtain superior results by
> eliminating more candidates at once?

My guess is that (my) Nanson is better than (my) Baldwin at social utility
because it eliminates candidates earlier in the process, when the Borda
scores are less distorted by the absence of previously eliminated
candidates, so Nanson winners tend to beat Baldwin winners on Borda score. 
But both methods distort Borda scores in later rounds, and a Baldwin winner
at least sometimes has a better initial Borda score than a Nanson winner;
try

 98:Abby>Cora>Erin>Dave>Brad
 64:Brad>Abby>Erin>Cora>Dave
 12:Brad>Abby>Erin>Dave>Cora
 98:Brad>Erin>Abby>Cora>Dave
 13:Brad>Erin>Abby>Dave>Cora
125:Brad>Erin>Dave>Abby>Cora
124:Cora>Abby>Erin>Dave>Brad
 76:Cora>Erin>Abby>Dave>Brad
 21:Dave>Abby>Brad>Erin>Cora
 30:Dave>Brad>Abby>Erin>Cora
 98:Dave>Brad>Erin>Cora>Abby
139:Dave>Cora>Abby>Brad>Erin
 23:Dave>Cora>Brad>Abby>Erin

Note that Nanson eliminates all candidates that couldn't possibly be
Condorcet winners based solely on Borda score.

=====
Rob LeGrand, psephologist
rob at approvalvoting.org
Citizens for Approval Voting
http://www.approvalvoting.org/

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