This paper examines how assumptions imposed on the data influence estimates
of schooling's effect on earnings. The paper models schooling decisions as
treatment effects and imposes assumptions about schooling selection to est
imate bounds on the treatment effect. The study begins by using the worst-c
ase bounds derived by Manski (1989, 1990, 1994, 1995) and adds assumptions
from the Roy model of schooling self-selection to narrow the bounds on the
schooling treatment effect. The bounds are narrowed further by using family
structure, college proximity, and school-quality characteristics as exclus
ion restrictions. The selection problem requires the researcher to make exp
licit assumptions to estimate the effect of schooling on earnings. This pap
er demonstrates that different selection assumptions yield very different r
esults.