Steven Brakman is Professor of International Economics at the University of Groningen, the Netherlands. He is co-author of The Economics of International Transfers (with C. van Marrewijk, 1998) and An Introduction to Geographical Economics (with C. van Marrewijk, H. Garretsen, 2001). Ben Heijdra is Professor of Macroeconomics at the University of Groningen, the Netherlands. He is the co-author (with Frederick van der Ploeg) of Foundations of Modern Economics (2002).