[영문]The labor force participation rate in the United States increased almost continuously for two-and-a-half decades after the mid-1960s, pausing only briefly during economic downturns. The pace of growth slowed considerably during the 1990s, however, and after reaching a record high of 67.3 percent in the first quarter of 2000, participation had declined by 1.5 percentage points by 2005. This paper reviews the social and demographic trends that contributed to the movements in the labor force participation rate in the second half of the twentieth century. It also examines the manner in which developments in the 2000s reflect a break from past trends and considers implications for the future.