Patent trolls on markets for technology - An empirical analysis of NPEs' patent acquisitions

Patent trolls, or NPEs, appropriate profits from innovation solely by enforcing patents against infringers. They are often characterized as relying on low-quality patents, an assessment that, if correct, would imply that eradicating such patents would effectively terminate the NPE business. In this paper, we shed light on this issue by empirically analyzing NPEs' patent acquisitions. We draw on a unique dataset of 392 U.S. patents acquired by known NPEs between 1997 and 2006, which we compare to three control groups of 784 U.S. patents each acquired by practicing firms. We find that the probability that a traded patent is acquired by an NPE rather than a practicing entity increases in the scope of the patent, in the patent density of its technology field and, contrary to common belief, in the patent's technological quality. Our findings thus support recent theoretical propositions about the NPE business model, showing that NPEs procure patents that are more likely to be infringed, harder to substitute for, and robust to legal challenges. The fact that NPE-acquired patents are of significantly higher quality than those in the control group implies that elevating minimum patent quality will not put an end to the NPE business, and suggests that this business is sustainable in the long run. We furthermore discuss the fact that NPEs are peculiar players on markets for technology insofar as they are solely interested in the exclusion right, not in the underlying knowledge. We posit that transactions involving NPEs may only be the tip of the iceberg of "patent-only" transactions, a conjecture with strong implications for the efficiency and the study of markets for technologies. Managerial and policy implications are discussed.