Changes in the work week drove a larger portion of changes in total labor input during the Great Depression of the 1930s than during other decades. Work-sharing policies appear to be responsible. Herbert Hoover created various work-sharing committees--led by key industrialists--which pushed for shorter work weeks. And Franklin Roosevelt's President's Reemployment Agreement called for sharp cuts in weekly work hours. Spreading available work amongst more people was the goal. During these periods between 50 and 90 percent of declines in labor input were accommodated by falling hours. In recent decades employers have instead relied on layoffs to achieve the same end.

We semiparametrically estimate average causal effects of different lengths of exposure to academic and vocational instruction in the Job Corps (JC) under the assumption that selection into different lengths is based on a rich set of observed covariates and time-invariant factors. We find that the estimated effects on future earnings increase in the length of exposure and that the marginal effects of additional instruction decrease with length of exposure. We also document differences in the estimated effects across demographic groups, which are particularly large between males and females. Finally, our results suggest an important lock-in effect in JC training. No rights reserved. This work was authored as part of the Contributor's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. law..