BUT WHY? The Urban Institute's C. Eugene Stuerle writes:

a postwar boom in the U.S. labor force is just now ending. Since around 1950, the percentage of adults who worked rose almost every year except in recessions. But now the great swell of working boomers is starting to retire, and most of the gain in female labor force participation is over. If Americans keep retiring at the same ages they do today, the share of adults who are working will fall markedly. The effect on the economy will be roughly equivalent to increasing the unemployment rate by 3/10 of 1 percent every year for 20 years straight starting in 2008.

He goes on to argue for older folks to remain in the workforce longer. I think, for a variety of reasons, that's a good outcome. The longer you work, the healthier, happier, richer and more mentally alert you tend to remain (though there are questions of correlation v. causation there). Nevertheless, a decrease in the number of workers, particularly as the boomers, who are fairly financially affluent, retire, may not be such a bad thing. The influx of women into the workforce and the postwar boom (along with other related factors, like the decline of unions, globalization, etc.) created something of a glutted labor market, leading to the rampant wage stagnation and reduced middle class buying power that began in the �70s. Reducing the supply of labor and tightening the market to the worker's benefit wouldn't be the worst thing in the world, and it may be the only politically realistic response to inequality hovering on the horizon.

--Ezra Klein