Top 50 words repeated twice, next 100 once, plus phrases. Participants emphasized repeatedly that much of the outcome of innovation accrues to society as spillover effects that present con- siderable measurement challenges. Adam Jaffe pointed out that among the advantages of patent data are that they are readily available, including on the Internet, contain considerable detail, and can be used to develop time series. The limitations of patent data are well known. Patents represent only a portion of innovative activity and none of the latter stage investments entailed in commer- cializing technology.
Patents are of widely varying value to firms.
The strengths and limitations of patent count data as an indica- tor of innovation output are summarized in the accompanying text box. The front page of U.S. patents contains citations of previous patents and other critical scientific literature purportedly representing the intellectual lineage or prior art of the patented invention and distinguishing it from previous inven- tions. For example, they are being used by Adam Jaffe and Francis Narin of CHI Research, Inc., as proxies of technical knowledge flows to assess firms' reliance on science and technology of the same or foreign national origins, on publicly versus privately funded research, and on particular public research spon- sors. The strengths and limitations of patent citation data as an indicator of knowl- edge flows are given in the text box. Aside from the limitations of patent data generally, this promising line of research is handicapped by a good deal of uncertainty about the origins and moti- vation of patent citations.