The paper seeks to understand the impact of the patent system on innovation by examining shifts in the strength of patent protection across sixty countries and a 150-year period. An examination of 177 policy changes reveals that changes in protection has a much greater effect on patenting by foreigners than on domestic entities. The author addresses concerns about the endogenously of these changes by employing an instrumental variable approach.
Link
http://www.dklevine.com/archive/leaner150yrs.pdf