Dominik Sachs

The COVID-19 pandemic has led to an increase in public debt in most countries, and the Ukraine war is likely to have similar effects. This will increase fiscal pressure in the future. We study how the shape of the optimal nonlinear income tax schedule is affected by this increase. We calibrate the workhorse optimal income tax model to five European countries: France, Germany, Italy, Spain and the UK. Applying an inverse-optimum approach to the pre COVID-19 economies we obtain the Pareto weights implicitly applied by the different countries. We then ask how the schedule of marginal and average tax rates should be optimally adjusted to the increase in fiscal pressure. For all countries, we find that the increase in fiscal pressure leads to a less progressive optimal tax schedule both in terms of marginal and average tax rates.

We analyze Pareto-efficient tax deduction rules for work-related expenses. Pareto efficiency dictates a strict rule for marginal deductions along the income distribution. An immediate implication is a recipe for designing Pareto-improving reforms. We apply our theory and simulate a Pareto-improving reform that introduces deductions for non-care household services (housekeeping, gardening, laundry) in the United States. The reform combines marginal deduction rates for household services between 55% and 85% with a slight increase in marginal tax rates.

We study the optimal design of student financial aid as a function of parental income. We derive optimal financial aid formulas in a general model. We estimate a model of selection into college for the United States that comprises multidimensional heterogeneity, endogenous parental transfers, dropout, labor supply in college, and uncertain returns. We quantify optimal financial aid in the estimated model and find it is strongly declining in parental income even without distributional concerns. Equity and efficiency go hand in hand.

The taxation of bequests can have a positive impact on the labor supply of heirs through wealth effects. This leads to an increase in labor income tax revenue on top of direct bequest tax revenue. We first show in a theoretical model that a simple back-of-the-envelope calculation, based on existing estimates for the reduction in earnings after wealth transfers, fails: the marginal propensity to earn out of un- earned income is not a sufficient statistic for the calculation of this effect because (i) heirs anticipate the reduction in net bequests and adjust their labor supply already prior to inheriting, and (ii) when bequest receipt is stochastic, even those who ex post end up not inheriting anything respond ex ante to the implied change in their distribution of net bequests. We quantitatively elaborate the size of the overall revenue effect due to labor supply changes of heirs by using a state of the art life-cycle model that we calibrate to the German economy. Besides the joint distribution of income and inheritances, quasi-experimental evidence regarding the size of wealth effects on labor supply is a key target for this calibration. We find that for each Euro of bequest tax revenue the government mechanically generates, it obtains an additional 9 Cents of labor income tax revenue (in net present value) through higher labor supply of (non-)heirs.

We study the incidence of nonlinear labor income taxes in an economy with a continuum of endogenous wages. We derive in closed form the effects reforming nonlinearly an arbitrary tax system, by showing that this problem can be formalized as an integral equation. Our tax incidence formulas are valid both when the underlying assignment of skills to tasks is fixed or endogenous. We show qualitatively and quantitatively that contrary to conventional wisdom, if the tax system is initially suboptimal and progressive, the general-equilibrium "trickle-down" forces may raise the benefits increasing the marginal tax rates on high incomes. We finally derive a parsimonious characterization of optimal taxes.

We study the implications of limited commitment on education and tax policies chosen by benevolent governments. Individual wages are determined by both innate abilities and education levels. Consistent with real world practices, the government can decide to subsidize different levels of education at different rates. The lack of commitment influences the optimal structure of education subsidies. The direction of the effect depends on the design of labor taxes. With linear labor tax rates and a transfer for redistribution, subsidies become more progressive. By contrast, if the government is only constrained by informational asymmetries when designing taxes, subsidies become more regressive.

We analyze optimal taxation of labor and capital income in a life cycle framework with idiosyncratic income risk and ex-ante heterogeneity. Tax instruments are simple in that they can only condition on current income. We provide a decomposition of labor income tax formulas into a redistribution and an insurance component. The latter is independent of the social welfare function and determined by the degree of income risk and risk aversion. The optimal linear capital tax is non-zero and trades off redistribution and insurance against savings distortions. Our quantitative results reveal that the insurance component contributes significantly to optimal labor income tax rates and provides a lower bound on optimal taxes. Optimal capital taxes are significant.

We study the optimal design of integrated education finance and tax systems. The distribution of wages is endogenously determined by the costly education decisions of heterogeneous individuals before labor market entry. Consistent with empirical evidence, this human capital investment decision is risky. We find that an integrated education and tax system in which the government provides education loans to young individuals coupled with income-contingent repayment can always be designed in a Pareto optimal way. We present a simple empirically driven application of the framework to US data in which individuals make a college entry decision. We find the optimal repayment schemes for college loans can be well approximated by a schedule that is linearly increasing in income up to a threshold and constant afterwards. So although the full optimum could lead to complicated non-linear schedules in theory, very simple instruments can replicate it fairly well. The welfare gains from income-contingent repayment are significant.

We derive a simple sufficient-statistics test for whether a nonlinear tax-transfer system is second-best Pareto efficient. If it is not, then it is beyond the top of the Laffer curve and there exists a tax cut that is self-financing. The test depends on the income distribution, extensive and intensive labor supply elasticities, and income effect parameters. A tax-transfer system is likely to be inefficient if marginal tax rates are quickly falling in income. We apply this test to the German tax-transfer system, and we find that the structure of effective marginal tax rates is likely to be inefficient in the region where transfers are phased out.