This paper introduces a new internationally comparable data set that permits an empirical investigation of the effects of patent law on innovation. The data have been constructed from the catalogues of two 19th century world fairs: the Crystal Palace Exhibition in London, 1851, and the Centennial Exhibition in Philadelphia, 1876. They include innovations that were not patented, as well as those that were, and innovations from countries both with and without patent laws. I find no evidence that patent laws increased levels of innovative activity but strong evidence that patent systems influenced the distribution of innovative activity across industries. Inventors in countries without patent laws concentrated in industries where secrecy was effective relative to patents, e.g., food processing and scientific instruments. These results suggest that introducing strong and effective patent laws in countries without patents may have stronger effects on changing the direction of innovative activity than on raising the number of innovations.
National Bureau of Economic Research Working Paper no. 9909, August 2003, p. 1