We analyze the optimal nonlinear income tax schedule when taxpayers earn multiple incomes and differ along many unobserved dimensions. We derive the necessary conditions for the government’s optimum using both a tax perturbation and a mechanism design approach, and show that both methods...

We analyze the optimal nonlinear income tax schedule when taxpayers earn multiple incomes and differ along many unobserved dimensions. We derive the necessary conditions for the government's optimum using both a tax perturbation and a mechanism design approach, and show that both methods produce...

This paper develops a machine-learning method that allows researchers to estimate heterogeneous treatment effects with panel data in a setting with many covariates. Our method, which we name the dynamic causal forest (DCF) method, extends the causal-forest method of Wager and Athey (2018) by...

Understanding the effectiveness of social distancing on the spread of COVID-19 is crucial to justify economically costly social distancing measures. We present a case study focusing on the three Scandinavian countries. Whereas Denmark and Norway imposed relatively strict measures, Sweden follows...

This paper studies the labor market effects of non-pharmaceutical interventions (NPIs) to combat the COVID-19 pandemic. We focus on the Nordic countries which showed one of the highest variations in NPIs despite having similar community spread of COVID-19 at the onset of the pandemic: While...

We study the effect of reforms that close loopholes in the enforcement of the dividend-withholding tax (DWT). We focus on a Danish reform enacted in 2016, and compare Denmark to its Nordic neighbors. Our main outcome of interest is the quantity of stocks on loan. Before the reform all Nordic...

This paper studies the design of tax systems that implement a planner's second-best allocation in a market economy. An example shows that the widely used Mirrleesian (1976) tax system cannot implement all incentive-compatible allocations. Hammond's (1979) principle of taxation proves that any...

We characterize the second-best allocation in a Mirrleesian optimal tax model where agents differ in multiple dimensions and the planner can tax multiple goods non-linearly. We develop a new method that allows us to solve the partial differential equations that describe the optimum regardless of...

We propose a new method, that we call an allocation perturbation, to derive the optimal nonlinear income tax schedules with multidimensional individual characteristics on which taxes cannot be conditioned. It is well established that, when individuals differ in terms of preferences on top of...

We study the optimal tax system when taxpayers earn different kinds of income by supplying different inputs. Imperfect substitution between inputs allows for general equilibrium effects. We consider any type of cross-base responses to tax changes such as income-shifting. Formalizing the tax...