Estimating the Effects of Length of Exposure to Instruction in a Training Program: The Case of Job Corps

Length of exposure to instruction in a training program is important in determining the labor market outcomes of participants. Employing methods to estimate the causal effects from continuous treatments, we provide insights regarding the effects of different lengths of exposure to academic and vocational instruction in Job Corps (JC)—America’s largest and most comprehensive job training program for disadvantaged youth. We semiparametrically estimate average causal effects (on the treated) of different lengths of exposure using the “generalized propensity score” 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 are increasing in the length of exposure—which is consistent with human capital accumulation—and that the marginal effects of additional instruction are decreasing 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. JEL Classification: I38, C21, J24