The Growing Complexity of the United States Patent System

In this Article, we compare a data set of 1000 U.S. patents issued between1996 and 1998 to a similarly random sample of 1000 patents issued twentyyears earlier, between 1976 and 1978. By studying the differences betweenthe groups, we can get a clear picture of how the patent system has changedover time. The results are dramatic. By almost any measure - subjectmatter, time spent in prosecution, number of prior art references cited,number of claims, number of continuation applications filed, number ofinventors - the patents issued in the late 1990s are more complex thanthose issued in the 1970s. While some of these effects are attributable tothe patenting of new technologies like biotechnology and software, unknownin the early 1970s, the increase in complexity is robust even across areasof technology. Further, the patent system in the 1990s is moreheterogeneous than it was in the 1970s. There are far greater differencesby area of technology and by nationality in how patents are beingprosecuted in the 1990s than there were in the 1970s. We explore a numberof possible explanations for these results, and discuss the policyimplications of the lack of uniformity that now characterizes our patentsystem.