title: Comparing IV With Structural Models: What Simple IV Can and Cannot Identify.
abstract: 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.
authors.affiliation: University of Chicago, University College Dublin, Cowles Foundation, Yale University, and the American Bar Foundation.
authors.forename: James J
authors.initials: JJ
authors.lastname: Heckman
authors.forename: Sergio
authors.initials: S
authors.lastname: Urzúa