TY  - JOUR
AU  - Heckman,James J.
AU  - Urzua,Sergio
TI  - Comparing IV With Structural Models: What Simple IV Can and Cannot Identify
JF  - National Bureau of Economic Research Working Paper Series
VL  - No. 14706
PY  - 2009
Y2  - February 2009
UR  - http://www.nber.org/papers/w14706
L1  - http://www.nber.org/papers/w14706.pdf
N1  - Author contact info:
James J. Heckman
Department of Economics
The University of Chicago
1126 E. 59th Street
Chicago, IL 60637
Tel: 773/702-0634
Fax: 773/702-8490
E-Mail: jjh@uchicago.edu

Sergio S. Urzua
Department of Economics
Northwestern University
2001 Sheridan Road
Evanston, IL 60208
Tel: 847/491-8213
Fax: 847/491-7001
E-Mail: s-urzua@northwestern.edu
AB  - This paper compares the economic questions addressed by instrumental variables estimators with those addressed by structural approaches. We discuss Marschak's Maxim: estimators should be selected on the basis of their ability to answer well-posed economic problems with minimal assumptions. A key identifying assumption that allows structural methods to be more informative than IV can be tested with data and does not have to be imposed.
ER  -