This is Volume 3 of the Handbook of Industrial Organization series (HIO). Volumes 1 & 2 published simultaneously in 1989 and many of the chapters were widely cited and appeared on graduate reading lists. Since the first volumes published, the field of industrial organization has continued to evolve and this volume fills the gaps. While the first two volumes of HIO contain much more discussion of the theoretical literature than of the empirical literature, it was representative of the field at that time. Since then, the empirical literature has flourished, while the theoretical...