This paper examines the global dynamics of income inequality, focusing on the interaction of inequalities within and between countries. Using data from the World Inequality Database, the World Bank, and the United Nations, the analysis reveals that global income disparities remain high, despite recent improvements driven by the economic growth in emerging economies. The paper introduces and applies the Rich-to-Poor Ratio (RTP) as a refined metric for assessing extreme income gaps. The findings demonstrate a strong and statistically significant correlation between within-country inequality and between-country inequality, particularly at higher levels of development, forming a U-shaped relationship. This co-movement is not monotonic, suggesting that countries with lower external gaps may converge further to the advanced top only at the expense of greater internal income inequalities. Overall, the results highlight the need for a holistic approach to inequality that addresses both national and global dimensions.
KeywordsGlobal Income InequalitiesWithin CountriesBetween CountriesProcesses of Globalisation
Abbas, Z., Afshan, G., & Mustifa, G. (2022). The Effect of Financial Development on Economic Growth and Income Distribution: An Empirical Evidence from Lower-Middle and Upper-Middle-Income Countries. Development Studies Research, 9, 117-128. https://doi.org/10.1080/21665095.2022.2065325
Ahmed, A., Bussolo, M., Cruz, M., Go, D. S., & Osorio-Rodarte, I. (2020). Global Inequality in a More Educated World. The Journal of Economic Inequality, 18, 585-616. https://doi.org/10.1007/s10888-020-09440-z
Alvaredo, F., Chancel, L., Piketty, T., Saez, E., & Zucman, G. (2018). World Inequality Report 2018 . World Inequality Lab.
Alvaredo, F., Chancel, L., Piketty, T., Saez, E., & Zucman, G. (2020). Towards a System of Distributional National Accounts: Methods and Global Inequality Estimates from WID.world. Economics and Statistics, 517 ‑ 519 , 41-59. https://doi.org/10.24187/ecostat.2020.517t.2018
Bhandari, L., Debroy, B., Huang, J., Rozelle, S., & Yang, J. (2006). Rapid Growth of Selected Asia n Economies. Lessons and Implications for Agriculture and Food Security: China and India . Policy Assistance Series 1/2, RAP Publication.
Bosmans, K., Decancq, K., & Decoster, A. (2014). The Relativity of Decreasing Inequality between Countries. Economica, 81, 276-292. https://doi.org/10.1111/ecca.12059
Bourguignon, F. (2021). A Turning Point in Global Inequality … and Beyond . Institute for Advance Study.
Caraballo, M. Á., Dabús, C., & Delbianco, F. (2017). Income Inequality and Economic Growth Revisited. A Note. Journal of International Development, 29, 1025-1029. https://doi.org/10.1002/jid.3300
Chancel, L., & Piketty, T. (2021). Global Income Inequality, 1820-2020: The Persistence and Mutation of Extreme Inequality. Journal of the European Economic Association, 19, 3025-3062. https://doi.org/10.1093/jeea/jvab047
Chancel, L., Piketty, T., Saez, E., & Zucman, G. (2022). World Inequality Report 2022 . World Inequality Lab.
Cingano, F. (2014). Trends in Income Inequality and Its Impact on Economic Growth . OECD Social, Employment and Migration Working Papers, No. 163, OECD Publishing.
Cobham, A., & Sumner, A. (2014). Is Inequality All about the Tails? The Palma Measure of Income Inequality. Significance, 11, 10-13. https://doi.org/10.1111/j.1740-9713.2014.00718.x
Cobham, A., Schlögl, L., & Sumner, A. (2016). Inequality and the Tails: The Palma Proposition and Ratio. Global Policy, 7, 25-36. https://doi.org/10.1111/1758-5899.12320
Conceição, P. N., & Ferreira, P. M. (2000). The Young Person ’ s Guide to the Theil Index: Suggesting Intuitive Interpretations and Exploring Analytical Applications . UTIP Working Paper Number 14. https://doi.org/10.2139/ssrn.228703
Crawley, H., Garba, F., & Nyamnjoh, F. (2022). Migration and (In)Equality in the Global South: Intersections, Contestations and Possibilities: Editorial Introduction. Zanj: The Journal of Critical Global South Studies, 5, 1-13.
Davies, J., & Shorrocks, A. (2021). Comparing Global Inequality of Income and Wealth. In C. Gradín, M. Leibbrandt, & F. Tarpa (Eds.), Inequality in the Developing World (pp. 49–73). Oxford University Press. https://doi.org/10.1093/oso/9780198863960.003.0003
de Haan, J., & Sturm, J. (2017). Finance and Income Inequality: A Review and New Evidence. European Journal of Political Economy, 50, 171-195. https://doi.org/10.1016/j.ejpoleco.2017.04.007
Deaton, A. (2021). COVID-19 and Global Income Inequality . Working Paper 28392, National Bureau of Economic Research, Massachusetts Avenue, Cambridge, MA.
Dorn, F., Fuest, C., & Potrafke, N. (2017). Globalisation and Income Inequality Revisited. Fellowship Initiative “ Challenges to Integrated Markets ” . Discussion Paper 056, European Commission, Directorate-General for Economic and Financial Affairs. https://doi.org/10.2139/ssrn.3143398
European Commission (2023). Addressing Economic Inequalities . https://ec.europa.eu/social/main.jsp?catId=1593&langId=en
European Commission (2024). Forging a Sustainable Future Together: Cohesion for a Competitive and Inclusive Europe . Report of the High-Level Group on the Future of Cohesion Policy, February 2024. https://op.europa.eu/en/publication-detail/-/publication/c6e97287-cee3-11ee-b9d9-01aa75ed71a1/language-en
Fleurbaey, M., & Klasen, S. (2016). Inequalities and Social Progress in the Future. In World Social Science Report, 2016: Challenging Inequalities; Pathways to a Just World . UNESCO Publishing.
Greene, W. H. (2018). Econometric Analysis (8th ed.). Pearson.
Haughton, J., & Khandker, S. R. (2009. The Handbook on Poverty and Inequality . The World Bank.
Heimberger, P. (2020). Does Economic Globalisation Affect Income Inequality? A Meta‐analysis. The World Economy, 43, 2960-2982. https://doi.org/10.1111/twec.13007
Hujo, K. (2021). Social Protection and Inequality in the Global South: Politics, Actors and Institutions. Critical Social Policy, 41, 343-363. https://doi.org/10.1177/02610183211009899
Im, K. S., Pesaran, M. H., & Shin, Y. (2003). Testing for Unit Roots in Heterogeneous Panels. Journal of Econometrics, 115, 53-74. https://doi.org/10.1016/s0304-4076(03)00092-7
Kanbur, R. (2019). Inequality in a Global Perspective. Oxford Review of Economic Policy, 35, 431-444. https://doi.org/10.1093/oxrep/grz010
Klasen, S. (2016). What to Do abou t Rising Inequ ality in Developing Countries ? PEGNet Policy Brief, No. 5/2016, Kiel Institute for the World Economy (IfW), Poverty Reduction, Equity and Growth Network (PEGNet).
Levin, A., Lin, C. F., & Chu, C. S. J. (2002). Unit Root Tests in Panel Data: Asymptotic and Finite-Sample Properties. Journal of Econometrics, 108, 1-24. https://doi.org/10.1016/s0304-4076(01)00098-7
Milanovic, B. (2011). A Short History of Global Inequality: The Past Two Centuries. Explorations in Economic History, 48, 494-506. https://doi.org/10.1016/j.eeh.2011.05.001
Milanovic, B. (2013). Global Income Inequality in Numbers: In History and Now. Global Policy, 4, 198-208. https://doi.org/10.1111/1758-5899.12032
Milanovic, B. (2022). The Three Eras o f Global Ineq uality, 1820-2020 with the Focus on the Past Thirty Yea rs . Stone Center on Socio-Economic Inequality, Working Paper Series.
OECD (2016). Indexes and Estimation Techniques. OECD Regions at a Glance 2016 . OECD Publishing.
OECD (2022). OECD Regions and Cities at a Glance 2022 . OECD Publishing.
Ortiz, I., & Cummins, M. (2011). Global Inequality: Beyond the Bottom Billion — A Rapid Review of Income Distribution in 141 Countries . UNICEF. https://doi.org/10.2139/ssrn.1805046
Osakwe, P. N., & Solleder, O. (2023). Understanding the Drivers o f Income Inequalit y within and across Countries : Some New Evid ence . United Nations Conference on Trade and Development, Working Paper n. 2, UNCTAD/WP/2023/1.
Palma, J. G., & Stiglitz, J. E. (2016). Do Nations Just Get the Inequality They Deserve? The “Palma Ratio” Re-Examined. In Inequality and Growth: Patterns and Policy (pp. 35-97). Palgrave Macmillan UK. https://doi.org/10.1057/9781137554598_2
Peterson, E. W. F. (2017). Is Economic Inequality Really a Problem? A Review of the Arguments. Social Sciences, 6, Article No. 147. https://doi.org/10.3390/socsci6040147
Petrakos, G., Tsiapa, M., & Kallioras, D. (2024). Business Cycles and Income Inequalities i n the EU. DLV 1.2, Economic, Social and Spatial Inequalities in Europe in the Era o f Global Mega-Trends . ESSPIN, Project 101061104, HORI-ZON-CL2-2021-Transformations-01.
Piketty, T. (2014). The Capital in the 21st Century . Harvard University Press.
Piketty, T., Saez, E., & Zucman, G. (2018). Distributional National Accounts: Methods and Estimates for the United States. The Quarterly Journal of Economics, 133, 553-609. https://doi.org/10.1093/qje/qjx043
Seo, H.‑J., Kim, H. S., & Lee, Y. S. (2020). The Dynamic Relationship between Inequality and Sustainable Economic Growth. Sustainability, 12, Article No. 5740. https://doi.org/10.3390/su12145740
Taconet, N., Méjean, A., & Guivarch, C. (2020). Influence of Climate Change Impacts and Mitigation Costs on Inequality between Countries. Climatic Change, 160, 15-34. https://doi.org/10.1007/s10584-019-02637-w
Tica, J., Globan, T., & Arčabić, V. (2021). Managing the Impact of Globalization and Technology on Inequality. Economic Research- Ekonomska Istraživanja , 35, 1035-1060. https://doi.org/10.1080/1331677x.2021.1952466
United Nations (2020). Inequality — Bridging the Divide .
United Nations (2023a). Progress towards the Sustainable Development Goals: Towards a Rescue Plan for People and Planet (Special ed.). Report of the Secretary-General.
United Nations (2023b). The Sustainable Development Goals Report (Special ed.).
United Nations University (2021). Trends in Global Inequality — A Comprehensive Ap proach . Research Brief.
Vo, D. H., Nguyen, T. C., Tran, N. P., & Vo, A. T. (2019). What Factors Affect Income Inequality and Economic Growth in Middle-Income Countries? Journal of Risk and Financial Management, 12, Article No. 40. https://doi.org/10.3390/jrfm12010040