Knowledge that Transforms

In October 2007, France introduced an exemption on the income tax and social security contributions that applied to wages received for hours worked overtime. The goal of the policy was to increase the number of hours worked. This article shows that this reform has had no significant impact on hours worked. Conversely, it has had a positive impact on the overtime hours declared by highly qualified wage earners, who have opportunities to manipulate the overtime hours they declare in order to optimize their tax situation since the hours they work are difficult to verify.

This paper provides among the first rigorous estimates of the labor-market returns to community college certificates and diplomas, as well as estimating the returns to the more commonly-studied associate's degrees. Using administrative data from Kentucky, we estimate panel-data models that control for differences among students in pre-college earnings and educational aspirations. Associate's degrees and diplomas have quarterly earnings returns of nearly $2,400 for women and $1,500 for men, compared with much smaller returns for certificates. There is substantial heterogeneity in returns across fields of study. Degrees, diplomas, and - for women - certificates correspond with higher levels of employment.

In the 1980s, many US cities initiated programs reserving a proportion of government contracts for minority-owned businesses. The staggered introduction of these set-aside programs is used to estimate their impacts on the self-employment and employment rates of African American men. Black business ownership rates increased significantly after program initiation, with the black-white gap falling 3 percentage points. The evidence that the racial gap in employment also fell is less clear as it depends on assumptions about the continuation of preexisting trends. The black gains were concentrated in industries heavily affected by set-asides, and they mostly benefited the better educated.

We study the effectiveness of magnet programs in an urban district that ration excess demand by admission lotteries. Differential attrition arises since students who lose the lottery are more likely to pursue options outside the school district than students who win the lottery. When students leave the district, important outcome variables are often not observed. The treatment effects are not point-identified. We exploit known quantiles of the outcome distribution to construct informative bounds on treatment effects. We find that magnet programs improve behavioral outcomes but have no significant effect on achievement.

Military assignment mechanisms provide a unique opportunity to estimate the impact of high-performing mentors on job advancement of their subordinates. Combining US Army administrative data with officer evaluation reports, we find that high-performing mentors positively affect early junior officer promotion and that early promotion probabilities rise as the duration of the high-quality mentorship increases. These effects are largest for high-ability protégés. Junior officers who were exposed to multiple high-performing mentors did not experience an additional increase in promotion rates.

Unlike in elementary school, high school teacher effects may be confounded with both selection to tracks and track-level treatments. I document confounding track effects and show that traditional tests for the existence of teacher effects are biased. After accounting for biases, high school algebra and English teachers have smaller test score effects than found in previous studies and value-added estimates are weak predictors of teachers’ future performance. Results indicate that either (a) teachers are less influential in high school than in elementary school or (b) test score effects are a weak measure of teacher quality at the high school level.