By Juergen Jung and Chung Tran
We study the optimal progressivity of personal income taxes in an environment where individuals are exposed to idiosyncratic shocks to health and labor productivity over the lifecycle. Our analysis is based on a large-scale overlapping generations general equilibrium model that is calibrated to the US economy. Our results indicate that the presence of health risk and health insurance has a strong effect on the amount of redistribution and social in- surance provided by progressive income taxes. In an environment with a non-universal health insurance system, such as the US system, the optimal income tax system is highly progressive in order to provide a sufficient level of redistribution to unhealthy low income individuals. The total welfare gain from optimizing the progressivity level is 5.6 percent in compensating lifetime consumption. More inclusive health insurance systems, such as Medicare for all, lead to large decreases in the optimal level of tax progressivity. When health expenditure risk is eliminated, the optimal income tax code becomes more similar to the findings of previous studies that used models without health risk. Our findings highlight the quantitative importance of accounting for the interdependence of health insurance and income taxes when designing optimal income tax policies.
There is quite a bit of discussion these days on the progressivity of US taxes. When comparing it to other countries, and possibly across time as well, it is important to also consider the impact of government benefits as well. On top of that, this paper shows that health insurance coverage is a major factor as well. This is indeed a complicated question.