Pioneers, Submariners, or Thicket-builders: Which Firms Use Continuations in Patenting?
---- Acknowledgements -----
We thank Bronwyn Hall and Bhaven Sampat for access to the Compustat database, and data on patent expiration and examiner-inserted citations respectively. We are grateful to Robert Barr and participants at the Spring 2007 Seminar on Innovation (University of California, Berkeley) for their helpful comments. Support for this research was provided by the Andrew W. Mellon and Ewing Marion Kauffman Foundations. The views expressed herein are those of the author(s) and do not necessarily reflect the views of the National Bureau of Economic Research.