A Contribution to the Theory of Income Inequality

Abstract

This paper uses the Solow Model of economic growth to model the evolution of inequality over time. In steady state, differences in household saving rates generate differences in household capital income. Households that save more accumulate more capital and have higher steady-state income. Tax policy affects the distribution of income through its influence on household saving rates. Increasing the tax rate on labor income causes a greater percentage decrease in the steady-state saving rates of relatively low savers, thus increasing pre-tax income inequality. Conversely, increasing the tax rate on capital income reduces pre-tax income inequality because it causes a greater percentage decrease in the steady-state saving rates of relatively high savers. Empirical tests of the model using data from the March Current Population Survey and NBER’s TAXSIM model suggest that higher taxes on wage income are associated with higher levels of income inequality. A high degree of correlation among the average marginal tax rates prevents us from drawing inferences about the effect that taxation of capital income has on inequality.