Sunday, December 16, 2007

The IQ red herring

Post de Chris Dillow:

(...) why are many defenders of free markets so interested in IQ?

Leftists would reply that there's an ideological motivation at work - the belief that inequalities of income are legitimate if they can be shown to result from natural differences in IQ.

But I can't believe that this is the reason, because this is a howling error.

First, the correlation between IQ and earnings is low. This review (pdf) of the literature estimated that a on standard deviation difference in cognitive skills is associated with only a 10% difference in wages.

Such a small effect surely accords with common sense. You only have to look at you boss to see that the link between IQ and success is weak. Even if we ignore rent-seeking, height, beauty, luck and incentive-enhancing preferences (pdf), lots of things make for high earnings: hard work, creativity, interpersonal skills. And these have little relationship with IQ.

Dois comentários: ao contrário do que Chris Dillow escreve, não sei se "criatividade" não terá uma relação positiva o QI; por outro lado, tambem não me admirava se as "competências interpessoais" tivessem uma relação negativa com o QI, pelo que estes dois factores (se realmente se verificarem) talvez se anulem um ao outro.

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