In the coming half-century, the proportion of elderly in the populations of developed nations will nearly double, challenging the sustainability of old-age pensions and health care. This book examines the extent of that challenge and offers alternative probabilistic forecasts for the Group of Seven industrial nations (Canada, France, Germany, Italy, Japan, United Kingdom, United States). It examines the potential maximum life span, surveys life-extending medical advances, and considers the question of whether new breakthroughs will increase or decrease the costs of medical care.