TY  - JOUR
AU  - Dehejia,Rajeev H.
AU  - Wahba,Sadek
TI  - Propensity Score Matching Methods for Non-experimental Causal Studies
JF  - National Bureau of Economic Research Working Paper Series
VL  - No. 6829
PY  - 1998
Y2  - December 1998
UR  - http://www.nber.org/papers/w6829
L1  - http://www.nber.org/papers/w6829.pdf
N1  - Author contact info:
Rajeev H. Dehejia
Wagner School of Public Policy
New York University
295 Lafayette Street, 2nd floor
New York, NY 10012
Tel: 212-998-7435
E-Mail: rajeev@dehejia.net
AB  - This paper considers causal inference and sample selection bias in non-experimental settings in which: (i) few units in the non-experimental comparison group are comparable to the treatment units, and (ii) selecting a subset of comparison units similar to the treatment units is difficult because units must be compared across a high-dimensional set of pre-treatment characteristics. We propose the use of propensity score matching methods and implement them using data from the NSW experiment.  Following Lalonde (1986), we pair the experimental treated units with non-experimental comparison units from the CPS and PSID and compare the estimates of the treatment effect obtained using our methods to the benchmark results from the experiment.  We show that the methods succeed in focusing attention on the small subset of the comparison units comparable to the treated units and, hence, in alleviating the bias due to systematic differences between the treated and comparison units.
ER  -