the fiscal policy in the State party, such as the increase in the threshold for the payment of inheritance tax and the increase of the value added tax, as well as the gradual reduction of the tax on corporate incomes, are having on the ability of the State party to address persistent social inequality and to collect sufficient resources to achieve the full realization of economic, social and cultural rights for the benefit of disadvantaged and marginalized individuals and groups".17 b) Progressivity properly understood Three remarks are in order, however. First, it is important to relate progressivity in taxation schemes with the scope and content of the redistributive policies adopted within each country. A progressive tax system only can have an impact on the reduction of inequalities if the revenue from the taxes collected is redistributed through social policies that benefit the poor, rather than being spent on investments that shall only allow the rich to become richer. For the effective realization of economic, social and cultural rights, it is the combination of revenue mobilization and of spending choices that matters, and neither of these two elements alone shall in itself suffice to assess whether the efforts of the State are sufficient: just like one can easily imagine a State with generous social policies addressed at tackling poverty, but in which such policies are essentially financed by the poor themselves,18 it is possible to have a State tax the rich but not use the revenues collected in ways that have a significant impact on the reduction of inequalities. Secondly, the ability for even a progressive tax system to reduce inequalities depends not only on the contribution of the richest part of the population to public revenue in percentage terms, but also on the absolute levels of such contributions : if, for example, the richest decile of the population pays 90 per cent of the total income taxes collected in the country, the taxation system may be said to be progressive according to the most common measure of tax progressivity known as the Kakwani index. But if those richest 10 per cent are taxed at very low rates, the redistributive capacity of the taxation remains very limited: such a redistributive capacity is captured by another index, known as the Reynolds-Smolensky index, which measures the difference in income distribution before and after the tax is imposed.19 One important consequence of this distinction is that a tax reform that may at first appear as regressive because the proportion of the total tax revenue paid by the richest part of the population will decrease (leading, in other terms, the effort to be spread across a larger part of the population), nevertheless may have progressive consequences if the overall tax rates and thus the revenue the State may mobilize are increased. Thirdly, the introduction of a progressive taxation scheme could have counter-productive impacts if it resulted in choking the economy and significantly slowing down economic activity, thus, in the mediumto long-term, destroying the very revenue base the State may be able to count on in order to finance its 17 Committee on Economic, Social and Cultural Rights, Concluding Observations: the United Kingdom of Great Britain and Northern Ireland, E/C.12/GBR/CO/6 (14 July 2016), para. 16. 18 See, e.g., Report of the Special Rapporteur on the right to food, Olivier De Schutter, to the thirteenth session of the Human Rights Council, Addendum: Mission to Brazil (12-18 October 2009) (A/HRC/13/33/Add.6), para. 36: "The tax structure in Brazil remains highly regressive. Tax rates are high for goods and services and low for income and property, bringing about very inequitable outcomes. [...] [W]hile the social programmes developed under the “Zero Hunger” strategy are impressive in scope, they are essentially funded by the very persons whom they seek to benefit, as the regressive system of taxation seriously limits the redistributive impact of the programmes. Only by introducing a tax reform that would reverse the current situation could Brazil claim to be seeking to realize the right to adequate food by taking steps to the maximum of its available resources". 19 The Kakwani and the Reynolds-Smolensky indexes appeared simultaneously in the economic literature : see Nanak C. Kakwani, "Measurement of Tax Progressivity: An International Comparison", The Economic Journal, vol. 87 (345) (1977): 71–80; and Morgan O. Reynolds and Eugene Smolensky, Public Expenditures, Taxes and the Distribution of Income: The United States, 1950, 1961, 1970 (New York, Academic Press, 1977). For a general presentation, see Jonathan Haughton and Shahidur Khandker, Handbook on Inequality and Poverty (Washington, D.C.: World Bank, 2009) (chap. 15: "The Effects of Taxation and Spending on Inequality and Poverty"). The reliance on these measures has been criticized on the ground that they fail to take into account the changes in revenue that may result from the introduction of tax reforms: see Santiago Díaz de Sarralde, Carlos Garcimartín and Jesús Ruiz-Huerta, "The paradox of progressivity in low-tax countries: income tax in Guatemala", CEPAL Review, n° 102 (Dec. 2010), pp. 85-99. 9 CRIDHO Working Paper 2017/1