Across Five Eras: Patent Enforcement in the United States 1929-2006

In this paper, we use univariate structural break analysis to estimate rates of patent enforcement in infringement suits in the United States over 1929-2006. We separately estimate rates of validity and infringement for series constructed with district court and appellate court decisions. We find multiple structural breaks in series of both validity and infringement, and find that the breaks do not coincide. Our most reliable results suggest the rate of validity falls around 1939 and rises around 1983, and that the rate of infringement rises around 1951 and falls around 1990. We estimate an overall rate of winning on both validity and infringement to be between 27-29% for all years except for 1939-51 (when it falls to about 20%) and 1983-90 (when it rises to nearly 50%).