This volume provides in-depth analysis of the many unknowns that are threatening pension plans around the world. Many see the lengthening human life span as a welcome development; nevertheless, longer time horizons also expose us to greater risk and reduce our ability to predict long-term returns. Matters such as longevity risk, capital market shocks, regulatory and political risk, and model risk all have profound consequences for the numerous stakeholders in the area of pension plans, such as plan participants, plan sponsors, regulators, and consultants. In this volume, the contributors analyze challenges to retirement sustainability and sketch several ways in which these risks can be managed and financed, with a view to building a more resilient retirement system.