Skilled Immigration and Innovation: Evidence from Enrolment Fluctuations in US Doctoral Programmes


  •  Corresponding author: Ahmed Mushfiq Mobarak, Yale School of Management, 135 Prospect Street, New Haven, CT 06520, USA. Email:

  • We thank the National Bureau of Economic Research (NBER) Innovation Policy and the Economy programme and the National Science Foundation SciSIP programme for financial support, the National Science Foundation Division of Science Resources and Statistics for providing data on Ph.D. recipients under a licensing agreement and Rich Beaudoin, James Choy and Christine Rohde for excellent research assistance. We are grateful to Martin Boileau, Lee Branstetter, Benjamin Jones, Fiona Scott-Morton, Stephen Redding, Mark Rosenzweig, Chris Udry, the editor Rachel Griffith, anonymous referees and seminar attendees at the NBER Innovation Policy and the Economy meetings, the NBER International Trade and Investment meetings, NBER Economics of Education Meetings, NSF SciSIP Conference, American Economic Association 2011 Annual Meetings, Duke University, Yale University and London School of Economics for helpful comments.


We study the contribution of doctoral students to innovation at 2,300 American science and engineering departments from 1973 to 1998. Macroeconomic and policy shocks in source countries that differentially affect enrolments across fields and universities isolate exogenous variation in the supply of students. Both US and international students contribute significantly to the production of knowledge at scientific laboratories, and their contributions are statistically comparable, consistent with an optimising department. A theoretical model of scholarships helps us to infer the productivity effects of student quality. Visa restrictions limiting entry of high-quality students are found to be particularly costly for academic innovation.