With the first Baby Boomers headed for retirement within a bare decade, worries are growing about the huge burden this group will place on the federal budget in the 21st century--and politicians are busy unveiling plans to keep Social Security and Medicare afloat.

How realistic are such fears? In a study in the Journal of Economic Perspectives, Ronald Lee of the University of California at Berkeley and Jonathan S. Skinner of Dartmouth College underscore the high degree of uncertainty attached to current demographic and economic projections.