Income vs. IQ

Robin Hanson (
Thu, 19 Jun 1997 10:08:08 -0700 (PDT)

The 13 June 97 Science, p 1651, mentions recent work by Murray on
Income as a function of IQ and age. Murray looks at 710 pairs of
siblings, now in their 30's who have been tracked since 1979. Each
pair has one normal IQ person (890-110) and either one dull person
(<90) or one bright person (>110). Graphing the average income of
these people as a function of time (and hence of subject's age),
Murray finds the income of all three groups stays low and the same for
about five years, then for the next six years the dull group gets a
lower income while the top two groups stay together, and then finally
the bright group splits off, ending with a income almost twice that of
the dull group.

Of course the article was interested in how much IQ variance
contributes to income inequality, but I started thinking about how
this time dependence would extend given longer lifespans. (Warning: I
never read the Bell Curve.)

Holding constant the IQ variance but extending lifespan, would income
variance at the end increase? That is, the longer time you have to
work and invest in learning things, the more benefit you can get out
of your higher IQ? Or would the same income variance spread out over
a longer time scale?

Varing the IQ variance for a fixed lifespan, is there some maximum IQ
beyond which IQ doesn't help income within the lifespan, so that
longer lifespans are required to take advantage of it?

Or am I tring to read too much into a few noisy data points?

Robin D. Hanson