소득불평등성, 누진성, 소득세집중도 및 사회후생에 대한 통합적 고찰

An Integrated Analysis on Income Inequality, Tax Progressivity, Concentration Coefficient for Income Tax, and Social Welfare in Korea

The purpose of this work is to develop the new measure of the after tax income inequality by introducing the explicit value judgement of income distribution in asociety, i.e., the equal marginal sacrifice principle. The newly derived I-index estimates the income inequality in terms of after-tax income. From this index of income inequality, the composite index of the progressivity of income tax is proposed. The new index of income inequality is linked into the social welfare function. The discussion of this paper is progressed toward the integrated approach of inequality, tax progressivity, and social welfare. By using the data on Family Income and Expenditure in Korea, new indexes of income inequality and tax progressivity are estimated, and the social welfare after income tax is measured during the period of 1991-1996. In Korea, the income tax progressivity increased according to the estimates of two composite indices and then after-tax income inequality on the basis of the I-index reduced, implying that after-tax income distribution in Korea has improved for five years. Also after-tax social welfare increased greatly during the five years. These estimated results are quite different from the previous ones in particular based on the Gini measure.