I have called this book Exploring the black box in order to emphasize its intellectual continuity with an earlier one, Inside the black box. In the preface to that book I stated that its purpose was “to break open and to examine the contents of the black box into which technological change has been consigned by economists” (p. vii). That statement of intent would also serve as a useful entry point into what follows. The economics of technological change is a subject that is still seriously befuddled by the failure to come to grips with the immense diversity of the contents of the black box. Readers of the earlier book will find inevitable shifts of priority and direction in this one. Nevertheless, the present work represents a continuation of the intellectual “unpacking” that was central to Inside the black box. Although economists are now, happily, devoting considerably more attention to the economic significance of technological phenomena, the marginal returns to further effort of that kind remain extremely high. My research over the past several years has been generously supported by the Technology and Economic Growth Program of the Stanford Center for Economic Policy Research, for which I am most grateful. Dr. Ralph Landau, the co-director of that program, has been a continuous source of stimulation and encouragement. I have learned a great deal from him about some of the complexities of the interface between technology and economics. I must also express my particular thanks to the indefatigable Scott Stern, who helped in numerous ways in preparing this book for publication.