The coming century stands to witness an extraordinary worldwide aging of the human population, and the emergence of aged societies will present citizens and policymakers around the world with challenges unknown to their predecessors. Will working populations support ever larger numbers of long-lived retirees? How will aging pressures affect national pension programs, health systems, and labor markets? Will an increasingly elderly world be capable of sustained economic growth and continuing progress against poverty? And what sorts of adjustments will pronounced population-aging require of our most basic social institutions, including the family? Ronald D. Lee of the University of California–Berkeley, one of the world’s leading demographers, will address these and other issues at the fourth Henry Wendt Distinguished Lecture at AEI.