[EM] Newbie de-lurks to propose a clone-proof Borda method

Ken Kuhlman kskuhlman at gmail.com
Tue May 24 13:34:33 PDT 2005

I've recently become interested in election methods, and have noticed that 
while the Borda count has been shown to have many desirable properties, it 
is customarily dismissed because of its susceptibility to clones. The method 
proposed below, which I call "Correlated Instant Borda Runoff," is basically 
a tweak of Baldwin to solve the clone problem. 

Individual ballots are scored according to the Borda count, and then all 
possible candidate pairs are ranked according to correlation. The Borda 
loser of highest correlated pair is eliminated, and the next round proceeds 
with the remaining candidates. 

Under this method, clones can be seen as a special case of correlated pairs 
(they're perfectly correlated), and so the Borda loser of a clone pair is 
eliminated immediately, before they can spoil the election. 

For example, consider an election between A, B, and C, where B & C are 

While Borda gives the election to B, CIBR recognizes BC as highly correlated 
(and thus a clone), and so eliminates C and declares the election a tie 
between A & B. 

Note that if the clones are transposed on the second ballot, as below: 

Then AB are clones as well, and the election becomes a three-way tie. (The 
Borda property of declaring symmetrical elections ties is retained under 
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