MICHAEL LAHR is Assistant Research Professor in the Center for Urban Policy Research at Rutgers, The State University. He has recently co-edited, with Ronald E. Miller, Regional Science Perspectives in Economics: A Festschrift in Memory of Benjamin H. Stevens. - ERIK DIETZENBACHER is Associate Professor of International Economics and Business, University of Groningen, The Netherlands and is currently editor of Economic System Research. His publications include the three-volume set Input-Output Analysis, co-edited with Heinz D. Kurz and Christian Lager, and numerous articles in economic journals. AE(00): Forewords by WALTER ISARD and ROBERT E. KUENNE