Across Five Eras: Patent Validity and Infringement Rates in US Courts, 1929-2006

We use structural break analysis to estimate rates of patent validity and infringement in decisions on the merits in U.S. courts over 1929-2006. We separately estimate these rates for district court and appeals court decisions. We find multiple structural breaks in both validity and infringement, and the breaks do not coincide. The rate of validity falls around 1939 and rises around 1983, while the rate of infringement rises around 1950 and falls around 1991. We argue that these breaks, and the variation across the implied five "eras" of decision standards, reflect political and legal innovations.