Citation frequency and the value of patented inventions

Through a survey, private economic value estimates were obtained on 964 inv entions made in the United States and Germany and on which German patent re newal fees were paid to full-term expiration in 1995. A search of subsequen t U.S. and German patents yielded counts of citations to those patents. Pat ents renewed to full-term were significantly more highly cited than patents allowed to expire before their full term. The higher an invention's econom ic value estimate was, the more the patent was subsequently cited.