This study generalises the tax progressivity index given in Kakinaka and Pereira (2006), which
is unlike the traditional measures of tax progressivity that rely on the idea of the Lorenz curve,
Gini coefficient, tax burdens and income distributions, can be computed on the basis of time
series aggregate data on taxes and GDP. The extended version proposed here is decomposable
into the tax progressivity indices for various components of tax and satisfies a number of desirable
properties, including additivity, inclusiveness, unit independence, monotonicity, homogeneity,
transfer principle and the principle of addition. The proposed index is applied to
Pakistan’s data over the 60 years period of 1960-2020 to investigate the nature of progressivity
in the tax system. The results show overall tax structure has remained progressive during the
entire period of analysis, but the degree of progressivity has declined over the years. The relatively
more progressive taxes are sales and direct taxes other than income tax, while the regressive
or less progressive taxes are federal excise and customs duty.
Keywords: Tax Structure, Lorenz Curve, Gini Coefficient.
