Robert Fenge is Senior Research Fellow at the Ifo Institute for Economic Research and Assistant Professor of Economics at the University of Munich. ierre Pestieau is Professor of Economics at the University of Liège. Fenge is coauthor (with Pierre Pestieau) of Social Security and Early Retirement (MIT Press, 2005).

Georges de Ménil is Professor of Economics at École des Hautes Études en Sciences Sociales (EHESS), Paris.

Pierre Pestieau is Professor of Economics at the University of Liège. Pestieau is coauthor (with Robert Fenge) of Social Security and Early Retirement (MIT Press, 2005).