References/Notes/Attributions:
Source
http://www.columbia.edu/~rd247/nswdata.html
References
Dehejia, R.H. and Wahba, S. 1999. Causal effects in non-experimental studies: re-evaluating the evaluation of training programs. Journal of the American Statistical Association 94: 1053-1062.
Lalonde, R. 1986. Evaluating the economic evaluations of training programs. American Economic Review 76: 604-620.