Patent assertion entities (commonly known as 'patent trolls') hurt competition and innovation. This book, the first to analyze the most salient issues related to patent assertion entities around the world, integrates economic theory with economic and legal reality to examine how the entities function and their impact on competition. It also offers legal and policy solutions that might be used to combat them. Edited by D. Daniel Sokol, the volume collects chapters from an array of leading scholars who describe patent assertion entities in the United States, Europe, Korea, Taiwan, Japan, and China, while offering empirical accounts of the entities' economic consequences and their use of litigation as a means of legal extortion against many of the most innovative companies in the world, from startups to multinationals. It should be read by anyone interested in how patent assertion entities operate and how they might be stopped.