TY  - JOUR
AU  - Angrist,Joshua D.
AU  - Imbens,Guido W.
TI  - Sources of Identifying Information in Evaluation Models
JF  - National Bureau of Economic Research Technical Working Paper Series
VL  - No. 117
PY  - 1991
Y2  - December 1991
UR  - http://www.nber.org/papers/t0117
L1  - http://www.nber.org/papers/t0117.pdf
N1  - Author contact info:
Joshua Angrist
Department of Economics
MIT, E52-353
50 Memorial Drive
Cambridge, MA  02142-1347
Tel: 617/253-8909
Fax: 617/253-1330
E-Mail: angrist@mit.edu

Guido Imbens
Department of Economics
Littauer Center
Harvard University
1805 Cambridge Street
Cambridge, MA 02138
Tel: 617/384-7485
Fax: 617/495-7730
E-Mail: imbens@fas.harvard.edu
AB  - The average effect of social programs on outcomes such as earnings is a parameter of primary interest in econometric evaluations studies. New results on using exclusion restrictions to identify and estimate average treatment effects are presented. Identification is achieved given a minimum of parametric assumptions, initially without reference to a latent index framework. Most econometric analyses of evaluation models motivate identifying assumptions using models of individual behavior. Our technical conditions do not fit easily into a conventional discrete choice framework, rather they fit into a framework where the source of identifying information is institutional knowledge regarding program administration. This framework also suggests an attractive experimental design for research using human subjects, in which eligible participants need not be denied treatment. We present a simple instrumental variables estimator for the average effect of treatment on program participants, and show that the estimator attains Chamberlain's semi-parametric efficiency bound. The bias of estimators that satisfy only exclusion restrictions is also considered.
ER  -