Stuart_Armstrong comments on Arrow's Theorem is a Lie - Less Wrong

27 Post author: alyssavance 24 October 2009 08:46PM

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Comment author: Stuart_Armstrong 26 October 2009 12:08:03PM *  1 point [-]

This voting system fails Pareto efficiency. Given three alternatives A, B and C, which I love, like, and hate respectively, I would vote 10-10-0. Get a second person like me, and we have options A and B equal even though we both prefer A.

And yes, this is a rational way of voting, if my dislike of C trumps any difference between A and B, and if I didn't know the preferences of the other voter.

Comment author: alyssavance 26 October 2009 06:35:09PM 4 points [-]

Again, that's not what Pareto efficiency means; it means that the voting algorithm will rank A higher if everyone votes A higher than B. Going by your definition, no voting algorithm could ever be Pareto efficient, because everyone could just lie and say they preferred B to A when it's actually the reverse.