The Elasticity of Taxable Income: The Case of South Africa

Abstract

AbstractA key tax policy parameter that has received much attention in the international literature, but about which there is substantial uncertainty, is the overall elasticity of taxable income. The size of this parameter is central to the formulation of tax and transfer policy, as well as for the study of the welfare implications of tax decisions. This paper uses a panel of individual tax returns for the period 2009–2013 and the phenomenon of “bracket creep” to construct instrumental variable estimates of the sensitivity of income to changes in tax rates. Estimates suggest that the overall elasticity of taxable income is approximately 0.3, while that of broad income is significantly lower. The overall response is primarily driven by the elastic response of taxable income for high‐income earners, who have an elasticity of closer to 0.4. Using the elasticity estimates within an optimal tax framework, it is determined that the optimal marginal tax rate for the top 10% of income earners is broadly in line with the current income tax schedule. However, results also suggest that there is little scope for raising marginal rates on high‐income earners further without inducing a negative revenue response.