Cumulative innovation is central to economic growth. Do patent rights facilitate or impede follow-on innovation? We study the causal effect of removing patent rights by court invalidation on subsequent research related to the focal patent, as measured by later citations. We exploit random allocation of judges at the U.S. Court of Appeals for the Federal Circuit to control for endogeneity of patent invalidation. Patent invalidation leads to a 50% increase in citations to the focal patent, on average, but the impact is heterogeneous and depends on characteristics of the bargaining environment. Patent rights block downstream innovation in computers, electronics, and medical instruments, but not in drugs, chemicals, or mechanical technologies. Moreover, the effect is entirely driven by invalidation of patents owned by large patentees that triggers more follow-on innovation by small firms.

We study the effects of the Medicines Patent Pool (MPP)—an institution that pools patents across geographical markets—on the licensing and adoption of life-saving drugs in low- and middle-income countries. We show the presence of an immediate and large increase in licensing when a patent is included in the MPP. We also show evidence that the pool increases actual entry and volume of sales, but these impacts are much smaller than on licensing, which is due to the geographic bundling of licenses. The paper highlights the potential of pools in promoting diffusion of biomedical innovation in developing countries.

We exploit historical data on planned highways, railroads, and exploration routes as sources of exogenous variation in order to estimate the effect of interstate highways on regional innovation: a 10% increase in a region's stock of highways causes a 1.7% increase in regional patenting over a five-year period. In terms of the mechanism, we report evidence that roads facilitate local knowledge flows, increasing the likelihood that innovators access knowledge inputs from local but more distant neighbors. Thus, transportation infrastructure may spur regional growth above and beyond the more commonly discussed agglomeration economies predicated on an inflow of new workers.