There is increasing empirical evidence that people systematically differ in their rates of return on capital. We derive optimal non-linear taxes on labor and capital income in the presence of such return heterogeneity. We allow for two distinct reasons why returns are heterogeneous: because individuals with higher ability obtain higher returns on their savings, and because wealthier individuals achieve higher returns due to scale effects in wealth management. In both cases, a strictly positive tax on capital income is part of a Pareto-efficient dual income tax structure. We write optimal tax rates on capital income in terms of sufficient statistics and find that they are increasing in the degree of return heterogeneity. Numerical simulations for empirically plausible return heterogeneity suggest that optimal marginal tax rates on capital income are positive, substantial, and increasing in capital income.

I derive the optimal nonlinear income tax when individuals do not necessarily maximize their own well-being. This generates a corrective argument for taxation: optimal marginal taxes are higher (lower) if individuals work too much (too little) from a well-being point of view. I allow for multi-dimensional heterogeneity and derive the optimal tax schedule in terms of measurable sufficient statistics. One of these statistics measures the degree to which individuals fail to optimize their labor supply. I empirically estimate this by using British life satisfaction data as a measure of well-being. I find that low-income workers tend to work 'too little' and high-income workers 'too much,' providing a motive for lower marginal tax rates at the bottom and higher marginal tax rates at the top of the income distribution

We analyse the redistributional (dis)advantages of a minimum wage over income taxation in competitive labour markets without imposing assumptions on the (in)efficiency of labour rationing. Compared to a distributionally equivalent tax change, a minimum‐wage increase raises involuntary unemployment, but also raises skill formation as some individuals avoid unemployment. A minimum wage is an appropriate instrument for redistribution if and only if the public revenue gains from additional skill formation outweigh both the public revenue losses from additional unemployment and the utility losses of inefficient labour rationing. We show that this critically depends on how labour rationing is distributed among workers. A necessary condition for the desirability of a minimum‐wage increase is that the public revenue gains from higher skill formation outweigh the revenue losses from higher unemployment. We write this condition in terms of measurable sufficient statistics.