Chapter 4 | Page 144 Personal income tax has long played a major role in developed countries, both as a source of government revenue and as an instrument for the redistribution of wealth.11 In many developing countries, personal income tax has played a much smaller part in raising revenue and reducing income inequality.12 Revenue from these taxes in most low-income countries is less than 10 percent, compared to more than 25 percent in the Organisation for Economic Co-operation and Development (OECD) countries.13 According to the International Monetary Fund (IMF), less than 5 per cent of the population in developing countries pays personal income tax, while the figure in developed countries is nearly 50 percent.14 Such a low level of personal income tax in developing countries not only represents a missed opportunity in terms of State revenue. Given the ineffectiveness of personal income tax regimes in many developing countries, it also means that the effect of these taxes on wealth redistribution and poverty reduction is minimal,15 which has an adverse effect on the realisation of ESC rights. Clearly, this is a fundamental area of tax policy that can have a significant positive impact on ESC rights resources, if properly designed and implemented. Potential revenue from personal income tax is also reduced in many developing countries due to high levels of tax evasion and avoidance.16 While many of the factors contributing to these distortions are often beyond the policy capacity of individual governments, simplifying personal income tax can be an important policy option for developing countries to increase their tax revenue. To address these challenges, some countries have already begun to simplify the personal income tax regime by levelling tax rate structures or by 11 Richard M Bird and Eric M Zolt, 'Redistribution via Taxation: the Limited Role of the Personal Income Tax in Developing Countries' (2014) UCLA Law Review. 12 Ibid. 13 Michael Keen, 'Taxation and Development - Again' (IMF Working Paper No WP/12/220, IMF, September 2012). 14 International Monetary Fund, 'Revenue Mobilization in Developing Countries' (Policy Paper, IMF, 8 March 2011) <http://www.imf.org/external/np/pp/eng/2011/030811.pdf>. 15 Bird and Zolt, above n 11. 16 International Monetary Fund, above n 14.