Saturday, December 29, 2007

The Condorcet Paradox

Another cool concept i took away from my negotiations class.... The Condorcet Paradox. Imagine a situation in which people have conflicting preferences. Is it possible to influence other's choices to reach an outcome which you prefer, while at the same time appearing fair and just? The answer is a clear "Yes". Condorcet paradox could come to your rescue. Let me explain with an example.

Suppose we have three candidates, A, B and C, and that there are three voters with preferences as follows (candidates being listed in decreasing order of preference):

Voter 1: A B C
Voter 2: B C A
Voter 3: C A B

Assume you are Voter 1, so you obviously want "A" to win. The condorcet strategy to reach this outcome is as follows:

1. Choose a strategy to eliminate out least preferred candidates.
2. Specifically, for the first step, choose the candidates other than "A".
3. Ask all the members to vote between "B" and "C".
4. Between "B" and "C", both voter 1 (you) and voter 2 prefer "B".
5. So, by a vote of majority "B" will get to stay and "C" is eliminated
6. Now again choose the elimination strategy between "A" and "B".
7. Both voter 1 (you) and voter 3, prefer "A" over "B".
8. So, by a vote of majority "A" will get to stay and "B" is eliminated.

Wow... you got what you wanted and at the same time appeared fair and just by taking majority votes all the time. Cool isn't it?

2 comments:

Random Hindustani said...

I think it'll be "B" instead of "C" in step 7...............

Rangarajan said...

Thanks Ozymandias... it was a typo. I just corrected it.