In this paper, we examine the heterogeneous treatment effects of a universal child care (preschool) program in Germany by exploiting the exogenous variation in attendance caused by a reform that led to a large staggered expansion across municipalities. Drawing on novel administrative data from the full population of compulsory school entry examinations, we find that children with lower (observed and unobserved) gains are more likely to select into child care than children with higher gains. This pattern of reverse selection on gains is driven by unobserved family background characteristics: children from disadvantaged backgrounds are less likely to attend child care than children from advantaged backgrounds but have larger treatment effects because of their worse outcome when not enrolled in child care.

Existing evidence on peer effects in the productivity of coworkers stems from either laboratory experiments or real-world studies referring to a specific firm or occupation. In this paper, we aim at providing more generalizable results by investigating a large local labor market, with a focus on peer effects in wages rather than productivity. Our estimation strategy—which links the average permanent productivity of workers' peers to their wages—circumvents the reflection problem and accounts for endogenous sorting of workers into peer groups and firms. On average over all occupations, and in the type of high-skilled occupations investigated in studies on knowledge spillover, we find only small peer effects in wages. In the type of low-skilled occupations analyzed in extant studies on social pressure, in contrast, we find larger peer effects, about one-half the size of those identified in similar studies on productivity. (JEL J24, J31, J41, M12, M54)

We analyze the impact of exercising sports during childhood and adolescence on educational attainment. The theoretical framework is based on models of allocation of time and educational productivity. Using the rich information from the German Socio-Economic Panel (GSOEP), we apply generalized ordered probit models to estimate the effect of participation in sport activities on secondary school degrees and professional degrees. Even after controlling for important variables and selection into sport, we find strong evidence that the effect of sport on educational attainment is statistically significant and positive. JEL Classification:I21, J13, J22, J24

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