Mothers' Labor Force Participation and the Availability of Part-Time Jobs

How does the structure of jobs in the labor market shape mothers' labor supply? In this paper, we show that mothers' labor force participation declines following a labor market shock that reduces the availability of part-time jobs, while fathers and women without children remain unaffected. We leverage an immigration reform that sharply increased the supply of high-skilled, full-time workers in a pre-defined set of border localities in Switzerland. Using social security registers and business census data in a difference-in-differences design, we show that the reform leads to a change in the structure of the labor market with fewer part-time jobs, resulting in a drop in mothers' labor force participation by 4 percentage points. This pattern translates into an increase in the “child penalty” that persists up to ten years after the birth of the first child. We provide evidence that mothers' drop-out is primarily driven by firms reducing their demand for part-time workers, thus highlighting a competition channel that manifests itself through the number of hours that workers are willing to supply. We rule out alternative mechanisms such as household income effects, fertility, and gender norms.