The effect of education on cognitive ability

We analyze whether the amount of schooling influences intelligence as measured by IQ tests. By use of a novel longitudinal dataset we are able to condition on early cognitive ability to account for selection into non-compulsory schooling when estimating the effect on cognitive ability at age 20. OLS estimates indicate that one year of schooling increases IQ by 2.8-3.5 points (about 0.2 standard deviations). When family income per family member and teacher evaluations of the individuals at age 10 are used as instruments for schooling and early cognitive ability, the return to schooling is estimated to 3.5-3.8 IQ points.