The participation rate, the share of the working-age population working or actively seeking a job, fell to 65.8 percent in January, the lowest reading in 17 years. There is debate among economists as to the reason for this decline. Some point to the loss of 2.8 million factory jobs over the last four years, where some people were unqualified to obtain other jobs. Other proposed reasons include people becoming discouraged and abandoning job searches because they can't find a job at the pay level they want, people choosing to go back to school, or become a stay-at-home mom or dad.
See "Working-Age People With Jobs on Decline", The New York Times, February 23, 2005