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...

The future of Social Security is troubled, both in the United States and in most other developed countries with aging populations. As improvements in health care and changes in life styles enable retirees to live longer than ever before, the stress on national budgets will increase...