The number of workers ages 75 and older increased 172% between 1977 and 2007.

Researchers at the federal Bureau of Labor Statistics have published that finding in a review of statistics on older workers.

Employment of U.S. residents 16 and older increased 59% during the 30-year period covered, and employment of U.S. residents ages 65 and over increased 101% during the span, the researchers write.

The increase in employment of the oldest workers reflects longevity and an increase in labor force participation rates, rather than the baby boom, because the oldest baby boomers are about 13 years away from reaching age 75.

The labor force participation rates for U.S. residents ages 65 and older fell to historic lows in the early 1990s, researchers note.