AxeI Borsch-Supan and Meinhard Miegel The provision of retirement income is a dynamic system that needs to be adapted constantly to the ever changing economic and societal environment. Sometimes, incremental adaptations suffice; sometimes, however, larger reform steps are necessary. We see this evolutionary process both through history and across countries. Over and again societies are confronted with new challenges, not the least with respect to old age social security. At this juncture of history, almost all industrialized countries face rapid population aging and need. to adapt their...