International inequality

International inequality refers to economic differences between countries. According to the United Nations Human Development Report 2004, the gross domestic per capita (GDP) in countries with high, medium and low human development (a classification based on the UN Human Development Index) was 24,806, 4,269 and 1,184 PPP$, respectively (PPP$ = purchasing power parity measured in United States dollars).

A study by the World Institute for Development Economics Research at United Nations University reports that the richest 1% of adults alone owned 40% of global assets in the year 2000, and that the richest 10% of adults accounted for 85% of the world total. The bottom half of the world adult population owned barely 1% of global wealth. In 2013, Oxfam International released a report to The World Economic Forum that the richest 1% owns 48 percent of the global wealth. In 2014, Oxfam reported that the 85 wealthiest individuals in the world have a combined wealth equal to that of the bottom 50% of the world's population, or about 3.5 billion people. More recently, in January 2015, Oxfam reported that the wealthiest 1 percent will own more than half of the global wealth by 2016.

The major component of the world's income inequality (the global Gini coefficient) is comprised by two groups of countries (called the "twin peaks" by Quah [1997]).

Economic inequality often closely matches a lognormal or Pareto distribution both across economies and within them.

The evolution of the income gap between poor and rich countries is related to convergence. Convergence can be defined as "the tendency for poorer countries to grow faster than richer ones and, hence, for their levels of income to converge". Convergence is a matter of current research and debate, but most studies have shown lack of evidence for absolute convergence based on comparisons among countries.

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