In this paper we use data on brothers, and fathers and sons, to estimate the economic
returns to schooling. Our goal is to determine whether the correlation between earnings and
schooling is due, in part, to the correlation between family backgrounds and schooling. The
basic idea is to contrast the differences between the schooling of brothers, and fathers and sons,
with the differences in their respective earnings. Since individuals linked by family affiliation
are more likely to have similar innate ability and family backgrounds than randomly selected
individuals our procedure provides a straightforward control for unobserved family attributes.
Our empirical results indicate that in the sample of brothers the ordinary least squares
estimates of the return to schooling may be biased upward by some 25% by the omission of
family background factors. Adjustments for measurement error, however, imply that the
intrafamily estimate of the returns to schooling is biased downward by about 25% also, so that
the ordinary least squares estimate suffers from very little overall bias. Using data on fathers
and sons introduces some ambiguity into these findings, as commonly used specification tests
reject our simplest models of the role of family background in the determination of earnings.

Although schooling and earnings are highly correlated, social
scientists have argued for decades over the causal effect of education. A
convincing analysis of the causal link between education and earnings
requires an exogenous source of variation in education outcomes. This
paper explores the use of college proximity as an exogenous determinant of
schooling. An examination of the NLS Young Men Cohort reveals that men who
grew up in local labor markets with a nearby college have significantly
higher education and significantly higher earnings than other men. The
education and earnings gains are concentrated among men with poorly-
educated parents -- men who would otherwise stop schooling at relatively
low levels. When college proximity is taken as an exogenous determinant of
schooling the implied instrumental variables estimates of the return to
schooling are 25-60% higher than conventional ordinary least squares
estimates.
Since the effect of a nearby college on schooling attainment varies by
family background it is possible to test whether college proximity is a
legitimately exogenous determinant of schooling. The results affirm that
marginal returns to education among children of less-educated parents are
as high and perhaps much higher than the rates of return estimated by
conventional methods.