Are Ideas Getting Harder to Find?
NBER Working Paper No. 23782
---- Acknowledgements ----
We are grateful to Daron Acemoglu, Philippe Aghion, Ufuk Akcigit, Michele Boldrin, Pete Klenow, Sam Kortum, Peter Kruse-Andersen, Rachel Ngai, Pietro Peretto, John Seater, Chris Tonetti, and seminar participants at the CEPR Macroeconomics and Growth Conference, George Mason, Harvard, the Minneapolis Fed, the NBER growth meeting, the NBER Macro across Time and Space conference, the Rimini Conference on Economics and Finance, and Stanford for helpful comments and to Antoine Dechezlepretre, Dietmar Harhoff, Wallace Huffman, Keith Fuglie, Unni Pillai, and Greg Traxler for extensive assistance with data. The Alfred Sloan Foundation and the European Research Council have provided financial support. An online data appendix with replication files can be obtained from http://web.stanford.edu/people/chadj. The views expressed herein are those of the authors and do not necessarily reflect the views of the National Bureau of Economic Research.