Typically, employment and the labour force include only work done for monetary gain. Hence, a homemaker is neither part of the labour force nor unemployed. Nor are full-time students nor prisoners considered to be part of the labour force or unemployment.[54] The latter can be important. In 1999, economists Lawrence F. Katz and Alan B. Krueger estimated that increased incarceration lowered measured unemployment in the United States by 0.17% between 1985 and the late 1990s.[54]