Annotation This is Vol 3 of the Handbook of Industrial Organization series (HIO). Vols 1 & 2 published simultaneously in 1989 under the editorship of Richard Schmalensee and Robert Willig. Many of the chapters in these successful volumes were widely cited and appeared on graduate reading lists, and some continue to appear even recently. Since the first volumes published, the field of industrial organization has continued to evolve. As the editors acknowledge in the Preface, these volumes had some gaps and this new volume aims to fill some of those gaps. The aim is to serve as a source, reference and teaching supplement for industrial organization, or industrial economics, the microeconomics field that focuses on business behavior and its implications for both market structures and processes, and for related public policies. The first two volumes of the HIO appeared at roughly the same time as Jean Tirole's book The Theory of Industrial Organization. Together they helped revolutionize the teaching of industrial organization, and provided a state-of-the-art summary. Tirole's book is concerned with the relevant theory, and several reviewers noted that the first two volumes of HIO contained much more discussion of the theoretical literature than of the empirical literature. In most respects, this imbalance was an accurate reflection of the field. Since then, the empirical literature has flourished, while the theoretical literature has continued to grow, and this new volume reflects that change of emphasis. *Part of the renown Handbooks in Economics series *Chapters are contributed by some of the leading experts in their fields. *A source, reference and teaching supplement for industrial organizations, or industrial economicists.