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...

In nearly every industrialized country, large aging populations and increased life expectancy have placed enormous pressure on social security programs—and, until recently, the pressure has been compounded by a trend toward retirement at an earlier age. With a larger fraction of the population...