Working Paper
The elasticity of taxable income

The elasticity of taxable income is a key tax policy parameter that plays an important role in the formulation of tax and transfer policy.

This paper extends work by Kemp (2019) by using a new panel of individual tax returns and the phenomenon of ‘bracket creep’ to produce updated estimates of the elasticity of taxable income for South Africa.

Whereas the previous work focused on assessed taxpayers (i.e. individual assessed tax returns), the current study uses a newly constructed panel for the period 2010–16 that includes information captured on both individual income tax return (ITR12) and employee tax certificate (IRP5) forms.

The elasticity of taxable income is estimated at around 0.4, somewhat higher than the estimate presented previously. The elasticity for broad income is estimated at around 0.2, similar in size to the earlier study.

As in that earlier study, it was found that behavioural responses are concentrated in higher-income groups, as suggested by the higher elasticity estimates for individuals in the top two income tax brackets and the top 10 per cent of income earners.

An important finding is that the ETI for high-income earners increases notably in the latter half of the sample, mainly due to increased itemized deductions in the face of a rising tax burden due to insufficient bracket adjustments and rising marginal rates.