have provided continuing guidance as we try to understand nanoscale science and technology well enough to measure and model its growth and commercialization. Evelyn Hu's detailed comments particularly improved the paper, and members of the UCLA Innovation Workshop also provided useful comments. We are indebted to Luis Arias, Chuling Chen, Rui Wu, and Josh Mason for their work on the nanotechnology data and analysis. This paper is a part of the NBER's research program in Productivity. Any opinions expressed are those of the authors and not those of their employers or the National Bureau of Economic Research.

The paper was improved by insightful comments from several discussants and anonymous referees. Certain data included herein are derived

Additional support for COMETS has been provided by The Ewing Marion Kauffman Foundation which both hosts the main COMETS site and in the past ran a COMETS Travel Grants Program to support early use of the COMETS data and presentation of resulting empirical research at conferences through direct grants to users. Certain data included herein are derived from the High

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