[Excerpt] The Congressional Budget Office (CBO) produces regular reports on the state of the U.S. economy and 10-year and longer-term projections of the nation’s budget and economic outlook. In producing those analyses, CBO examines many developments that could have short- or longer-term consequences for the budget and the economy. During the decades to come, one such development is expected to be a slower rate of growth of the labor force relative to the average growth rate of the past few decades. That slowdown is anticipated to occur primarily because of the aging and retirement of large numbers of baby boomers and because women’s participation in the labor force has leveled off since the late 1990s after having risen substantially throughout the three decades before that. This background paper describes the methods CBO uses to project such trends through 2021, updating CBO’s Projections of the Labor Force, a CBO Background Paper published in September 2004.