Capital Income Taxes With Heterogeneous Discount Rates

Peter A. Diamond Johannes Spinnewijn



With heterogeneity in both skills and preferences for the future, the Atkinson-Stiglitz result that savings should not be taxed with optimal taxation of earnings does not hold. Empirical evidence shows that on average people with higher skills save at higher rates. Saez (2002) suggests that with such positive correlation taxing savings can increase welfare. This paper analyzes this issue in a model with less than perfect correlation between ability and preference for the future. To have multiple types at the same earnings level, the number of types of jobs in the economy is restricted. Key to the analysis is that types who value future consumption less are more tempted to switch to a lower earning job. We show that introducing both a small savings tax on the high earners and a small savings subsidy on the low earners increase welfare, regardless of the correlation between ability and preferences for the future. This can be implemented by earnings varying rules on contributions to tax-favored retirement accounts. However, introducing a uniform savings tax, as in the Nordic dual income tax, increases welfare only if that correlation is succinctly high. There are also some results on optimal taxes that parallel the results on introducing small taxes.