This book is the idea of Scott Parris, economics editor in the United States for Cambridge University Press. Scott was infinitely patient, waiting for several years before the appearance of a mere outline of chapters, and then two more years before the introductions were written and submitted. Throughout, I have valued his cautionary advice about keeping the book to modest size and about what kinds of articles to include and exclude.

My greatest debt is to the sponsor of this research over a period of more than 30 years dating back to 1971, the National Science Foundation. I am very grateful to the late James Blackman, director of the Economics Program at the NSF from 1967 to 1980, both for support of my research and for inviting me to participate in the peer-review process as a member of the NSF economics panel during the period 1973–76. Since 1980, the NSF economics program has been co-directed with a sure hand by Dan Newlon and, until recently, Lynn Pollnow. I am especially grateful to Dan for frequent consultation and advice on the direction and progress of my research. The successive NSF grants have made possible the support of several generations of graduate and undergraduate research assistants at Northwestern University, some of whom are acknowledged in the initial footnotes of the chapters in this book, and many more of whom worked on papers that could not be included within the space constraints of this book.