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David Koll

Postdoctoral Scholar, University of Mannheim

Research Associate, EUI

Welcome!

I am a Postdoctoral Scholar at the University of Mannheim and a member of the Collaborative Research Center CRC TR 224 “Economic Perspectives on Societal Challenges” in project A03 with Michèle Tertilt.

I also work as a Research Associate at the European University Institute (EUI) with Philipp Kircher on his ERC-Project “Technological Change: New Sources, Consequences, and Impact Mitigation”.

I obtained a PhD in Economics at the EUI in September 2020. My supervisors were Árpád Ábrahám and Dominik Sachs.

My research fields are macroeconomics, labor and public economics.

Here is my CV.

Contact

  • Email:
    • koll at uni-mannheim.de
    • david.koll at eui.eu
  • Address:
    • Department of Economics, University of Mannheim
    • Room P.01
    • L7 3-5, 68131 Mannheim
  • Phone: +49 621 181-1959

Working Papers

Less money for divorced mothers? The child-age dependent reform of alimony in Germany

Using a large administrative panel dataset from Germany, we study the effect of a divorce law reform on the probability to pay alimony as a divorced father. The reform affected divorced couples differently depending on the age of their youngest common child. Using a difference-in-differences setup, we show that the reform decreased the probability to pay alimony if the youngest common child was between four and eight years old compared to the child being between sixteen and seventeen. Therefore, the reform decreased the disposable income of divorced, single mothers with younger children to a greater extent. Our results are robust to different empirical model and control group specifications. They also persist when we restrict the sample to those couples who got divorced before the reform. Furthermore, we show that the treatment intensity of the reform varies with the age of the youngest child having the largest impact if the child is between four and five.

The Fiscal Return to Childcare Policies

We study the long-term fiscal implications of childcare subsidies through their impact on maternal labour supply. Taking human capital accumulation into account, we explicitly capture life-cycle career aspects in a dynamic structural household model of female labour supply and childcare decisions: higher labour supply of mothers today results in higher expected future earnings. In our dynamic structural model, we allow households to be heterogeneous in their taste for home produced childcare, their taste for leisure, and in their access to informal childcare (e.g. by grandparents). Using German survey data, we provide a structural estimate of the degree to which childcare subsidies are dynamically self-financing through higher labour income tax revenue. Further, we explore how the marginal fiscal returns of childcare subsidies depend on the group of families targeted. Our estimates show that targeting childcare subsidies is a useful tool to increase the ability of these policies to be self-financing: an untargeted increase in childcare subsidies refinances itself by 2.6% over the remaining life cycle of the sampled households. The result increases to 17.4% (75.7%) if the subsidy is targeted towards (full-time) working mothers. Finally, targeting working mothers with children below the age of three raises the marginal return to 23.3%.

The Intergenerational Correlation of Employment: Mothers as Role Models

We document a substantial positive correlation of employment status between mothers and their children in the United States, linking data from the National Longitudinal Survey of Youth 1979 (NLSY79) and the NLSY79 Children and Young Adults. After controlling for ability, education, fertility, and wealth, a one-year increase in a mother’s employment is associated with, on average, six weeks more employment of her child. The intergenerational transmission of maternal employment is stronger to daughters than to sons, and it is higher for low-educated and low-income mothers. Investigating potential mechanisms, we provide evidence for a role-model channel, through which labor force participation is transmitted. Children, especially daughters, emulate the example of their mother when they observe her working. By contrast, we are able to rule out several alternative candidate explanations such as network effects, occupation-specific human capital and conditions within the local labor market.

On the Optimal Design of Income Transfer Programs: A Dynamic Perspective

I analyse optimal income transfer programs from a dynamic perspective within a stylised two-period model with extensive labor supply responses and add two features to the standard static model. First, human capital acquired by working increases future productivity. Second, working in the first period creates a higher attachment to the labor market via lower opportunity costs of work in the future. I derive the optimal participation tax formula of each period and express them in terms of sufficient statistics, i.e. semi-elasticities, social marginal welfare weights and dynamic fiscal revenue effects. I show that in income ranges, in which workers – by getting more productive – pay more taxes in period two compared to period one, in-work benefits will be partly self-financing. This especially implies compressed phase-in regions and longer phase-out regions of in-work benefits in the optimal tax schedule.