Demystifying inter-country inequality: Data, measures, and long-run trends in the inter-country and global distribution of human well-being

In this research I argue that past and future trends in inter-country and global inequality can be better explained and predicted by giving greater attention to key methodological and theoretical insights that span disciplinary boundaries. I propose a unifying framework for the study of inter-country inequality in non-pecuniary variables that explicitly links innovation diffusion to inequality and argues for a long-run view of world inequality trends. I suggest that the use of formal measures of inequality in the study of inequality trends for variables that are bounded or that can be expressed in complementary form (e.g. literacy and illiteracy) often violates the welfare and anonymity principles. Studies of convergence that rely on limited dependent variables are better served by the standard deviation than by conventional mean-standardized measures of inequality. To test these ideas, I collected national-level estimates of health (life expectancy at birth), fertility (crude birth rates and total fertility rates), education (primary school enrollment rates), income (GDP per capita), and population size for the majority of the world's countries and people going back to the early 1800s. Using these data, I provide long-run estimates of between-country inequality trends over most of the last two centuries. I find that the long-run inequality trends in key domains have followed a remarkably similar pattern of first rising and then falling inter-country inequality. In all three domains, inter-country inequalities were low in the early and mid 1800s, then began to rise through the early and mid 1900s. Between-country inequalities in fertility, health, and education have declined throughout much of the last half of the 20th century.