Since the publication of the first edition in 2005, questions of how to define and prove market power have continued to be at the forefront of antitrust issues considered in both merger and conduct investigations. Like the first edition, the second edition of The Market Power Handbook provides a comprehensive review of the legal and economic issues that arise in relation to the core antitrust concept of market power. It is designed to serve as a nontechnical resource rather than an economic text, but nonetheless provides an introduction to and summary of the economic concepts that are critical to an understanding of market power. The Handbook begins with the definition of market power and an introduction to the role market power plays in plays in cases brought under the principal antitrust statutes. Following chapters discuss the fundamental economic doctrines related to market power, the role of market power in market definition, and the measurement and interpretation of market shares and market concentration. The Handbook concludes with chapters discussing the characteristics of markets (such as differentiated products and barriers to entry) that affect the ability of firms to attain or exercise market power. Included in the Handbook are extensive discussions of issues such as the determination of whether market power exists in narrow product markets (often referred to as "submarkets"), the use of market power screens, "lock in" as a source of market power, and the analysis of market power in network markets. The second edition is updated to include discussions of the new 2010 Merger Guidelines and reflect the latest case law involving the issue of market power.