Link to September 3 Pew Research Center report, "Recession Turns a Graying Office Grayer".
Excerpt: The American work force is graying -- and not just because the American population itself is graying. Older adults are staying in the labor force longer, and younger adults are staying out of it longer. Both trends took shape about two decades ago. Both have intensified during the current recession. And both are expected to continue after the economy recovers. According to one government estimate, 93% of the growth in the U.S. labor force from 2006 to 2016 will be among workers ages 55 and older.
Demographic and economic factors explain some -- but not all -- of these changes. Attitudes about work also play an important role -- in particular, the growing desire of an aging but healthy population to stay active well into the later years of life