(1999). Citation Frequency and the Value of Patented Innovation Review of Economics and Statistics, 81 (3), 511-515.
Through a survey, private economic value estimates were obtained on 964 inventions made in the United States and Germany and on which German patent renewal fees were paid to full-term expiration in 1995. A search of subsequent U.S. and German patents yielded counts of citations to those patents. Patents renewed to full-term were significantly more highly cited than patents allowed to expire before their full term. The higher an invention's economic value estimate was, the more the patent was subsequently cited.
