Do Instrumental Variables Belong in Propensity Scores?
---- Acknowledgements -----
We thank Paul Rosenbaum, Frank Wolak, Salvador Navarro-Lozano, Azeem Shaikh, and Ed Vytlacil for helpful comments. Bhattacharya thanks the National Science Foundation and the National Institute on Aging for partially funding his work on this paper. All errors remain our own. The views expressed herein are those of the author(s) and do not necessarily reflect the views of the National Bureau of Economic Research.