Since the emergence of early endogenous growth models (Larry E. Jones and Rodolfo E. Manuelli, 1990; Sergio Rebelo, 1991), a large body of work has studied the growth effects of tax reform. While virtually all of this literature has confined itself to the analysis of flat-rate taxes, tax codes are generally progressive. This paper, therefore, explores the effects of progressive taxes in conventional growth models with heterogenous households. In such frameworks, the tax code helps to determine simultaneously the pre-tax income distribution and the rate of technical progress.

We present three main findings. First, we show that when variations in tax codes stem from differences in progressivity, shares of tax revenue in GDP or income may constitute poor proxies for average marginal tax rates. In particular, we find that the decrease in progressivity associated with the Tax Reform Act of 1986 (TRA-86) lowered the US average marginal tax rate by 0.06 to 0.37 percentage points depending on the model used. At the same time, however, the endogenous adjustment in the distribution of income produced by this progressivity change contributed to raising the tax share of income by approximately 0.8 percentage points. Because marginal tax rates are not easily observable, empirical work often has to make use of tax shares in income as an alternative. To the degree that lower marginal rates entail less tax distortion, our study suggests that relying on