Patent Enforcement and Innovation

This paper investigates the effect of patent protection on cumulative innovation. While one of the main functions of the patent system is to foster innovation, patents might block sequential innovation. Consequently, the actual impact of patent rights on innovation is still under debate. To investigate this relationship, I analyze the impact of patent infringement litigation on cumulative innovation. The results for a sample of U.S. patents imply that patent citations increase after a case is filed in a court. While citations increase during the litigation period, the relative effect size decreases in the years following the closure of the case. Further results imply that this effect is particularly driven by patents subject to litigation with a high degree of novelty and patents with a narrow breadth. Analyzing the impact of non-practicing entities shows that the change in citations is lower for patents owned by this type of patent holders. Moreover, citations of litigated patents stem particularly from patents that are close in terms of technological proximity and general similarity.