TY  - JOUR
AU  - Lee,David S.
TI  - Trimming for Bounds on Treatment Effects with Missing Outcomes
JF  - National Bureau of Economic Research Technical Working Paper Series
VL  - No. 277
PY  - 2002
Y2  - June 2002
UR  - http://www.nber.org/papers/t0277
L1  - http://www.nber.org/papers/t0277.pdf
N1  - Author contact info:
David Lee
Industrial Relations Section
Princeton University
Firestone Library A-16-J
Princeton, NJ 08544
Tel: 609/258-9548
Fax: 609/258-2907
E-Mail: davidlee@princeton.edu
AB  - Empirical researchers routinely encounter sample selection bias whereby 1) the regressor of interest is assumed to be exogenous, 2) the dependent variable is missing in a potentially non-random manner, 3) the dependent variable is characterized by an unbounded (or very large) support, and 4) it is unknown which variables directly affect sample selection but not the outcome. This paper proposes a simple and intuitive bounding procedure that can be used in this context. The proposed trimming procedure yields the tightest bounds on average treatment effects consistent with the observed data. The key assumption is a monotonicity restriction on how the assignment to treatment effects selection -- a restriction that is implicitly assumed in standard formulations of the sample selection problem.
ER  -