[EM] Correlated Instant Borda Runoff, without Borda

[Paul Kislanko]

Awhile back Dave Gamble and I speculated off-list that the "best" election
method would have each candidate fill out an extensive questionaire, and
have each voter fill out the same questionaire. Then a computer program
would find the best correlation between voters' answers and candidates'
answers. 
 
This has the distinct advantage that there would be no advertising,
campaigning, or opportunities for special interests to try to sway the
election. It has the obvious difficulty of defining and calculating the
"best correlation", which is probably impossible except in science fiction.
(It was Isaac Asimov's short story "Franchise" that led us down that path).


  _____  

From: election-methods-bounces at electorama.com
[mailto:election-methods-bounces at electorama.com] On Behalf Of Simmons,
Forest
Sent: Friday, December 23, 2005 3:18 PM
To: election-methods at electorama.com
Subject: Re: [EM] Correlated Instant Borda Runoff, without Borda


 Great ideas in a much neglected area!
 
A couple of comments:
 
1.  It seems to me that it is better to start by eliminating the pairwise
loser of the least (as opposed to most) correlated pair of candidates.  This
reduces burial incentive.
 
2.  These kinds of methods tend to lack monotonicity because increasing
support for a winner can change the correlations in such a way that the
winner faces an unfavorable pairwise contest that didn't materialized
before.
 
3.  To overcome the monotonicity problem, the correlation data could be
obtained separately from the rankings.  However, this tends to open up
opportunities for manipulations of the correlations, since they are not tied
to the rankings.
 
Taking into account (1), (2) and (3) I've come up with the following idea,
which I call "Narrowing In:"
 
(A)  Have the candidates fill out extensive questionnaires with a wide
variety of questions related to a wide variety of issues.
 
(B)  Publish their responses, as well as the correlations between the
candidates based on their responses.
 
(C)  Have the voters rank the candidates.
 
(D)  While there remain two or more candidates, eliminate the pairwise loser
of the least correlated pair.
 
Remarks:
 
Note that if issue space turns out to be essentially one dimensional, the
method starts eliminating candidates from the outside, narrowing in on the
Condorcet winner.
 
Because the candidates' responses to the questionnaire are published before
the vote, they have no (unusual) incentive to lie about their position on
the issues.
 
This method is monotone.  It has little incentive for favorite betrayal
since Favorite and Compromise tend to be highly correlated, so the decision
between them tends to come late in the game, if at all. 
 
 In fact, the only time there could be a favorite betrayal incentive is if
Compromise and Favorite formed the least correlated pair, while there still
remained at least one other candidate to be eliminated.  
 
Even then there would be no betrayal incentive if the pairwise winner of the
pair had has great a chance against the other remaining candidate(s) as the
pairwise loser of the pair.
 
What do you think?
 
Forest

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