William R. Kerr is professor at Harvard Business School and a research associate of the NBER. Joshua Lerner is the Jacob H. Schiff Professor of Investment Banking at Harvard Business School, with a joint appointment in the Finance and the Entrepreneurial Management Units, and a research associate and codirector of the Productivity, Innovation, and Entrepreneurship Program at the NBER. Scott Stern is the School of Management Distinguished Professor of Technological Innovation, Entrepreneurship, and Strategic Management at the Massachusetts Institute of Technology Sloan School of Management and a research associate and director of the Innovation Policy Working Group at the NBER.