Lanjouw, Jean O; Pakes, Ariel; Putnam, Jonathan - In: Journal of Industrial Economics 46 (1998) 4, pp. 405-32
Patent counts are very imperfect measures of innovative output. This paper discusses how additional data--the number of years a patent is renewed and the number of countries in which protection for the same invention is sought--can be used to improve on counts in studies that require a measure...