This is the introduction and summary to the fourth phase of an ongoing project on Social Security Programs and Retirement Around the World. The first phase described the retirement incentives inherent in plan provisions and documented the strong relationship across countries between social...

Many countries have social security systems that are currently financially unsustainable. Economists and policy makers have long studied this problem and identified two key causes. First, as declining birth rates raise the share of older persons in the population, the ratio of retirees to...