The labor force, which forms the denominator of the standard unemployment rate (also known as U-3), consists of all persons who are working or have actively looked for work in the preceding month. People who want a job, but have stopped working, are omitted from both the numerator and denominator. In a typical month, there are millions of such labor force dropouts, even though they are not reflected in the standard statistics.
In an effort to take at least some of those labor-force drop-outs into account, the BLS publishes a supplementary index known as U-5, which includes discouraged and marginally attached workers in both its numerator and denominator. These groups include all those who want a job and have looked for one within the past year, but not within the past month. Discouraged workers cite their belief that there are no jobs to be found as their reason for not looking for work. Marginally attached workers give other reasons, such as family responsibilities. People who say they want a job but have gone longer than a year without looking for one are not counted in either U-3 or U-5.