Economists often assume that a patent gives its owner a well-defined legal right to exclude others from practicing the invention described in the patent. In practice, however, the rights afforded to patent holders are highly uncertain. Under patent law, a patent is no guarantee of exclusion but more precisely a legal right to try to exclude. Since only 0.1% of all patents are litigated to trial, and since nearly half of fully litigated patents are declared invalid, this distinction is critical to understanding the economic impact of patents. The growing recognition among economists and legal scholars that patents are probabilistic property rights has significant implications for our understanding of patents in four important areas: (1) reform of the system by which patents are granted; (2) the legal treatment of patents in litigation; (3) the incentives of patent holders and alleged infringers to settle their disputes through licensing or cross-licensing agreements rather than litigate them to completion; and (4) the antitrust limits on agreements between rivals that settle actual or threatened patent litigation.
