In recent decades, income inequality has increased in nearly all countries, but at different speeds, suggesting that institutions and policies matter in shaping inequality.

• Since 1980, income inequality has increased rapidly in North America, China, India, and Russia. Inequality has grown moderately in Europe. From a broad historical perspective, this increase in inequality marks the end of a postwar egalitarian regime which took different forms in these regions.

• There are exceptions to the general pattern. In the Middle East, sub-Saharan Africa, and Brazil, income inequality has remained relatively stable, at extremely high levels. Having never gone through the postwar egalitarian regime, these regions set the world “inequality frontier.”

• The divergence in inequality levels has been particularly extreme between Western Europe and the United States, which had similar levels of inequality in 1980 but today are in radically different situations. While the top 1% income share was close to 10% in both regions in 1980, it rose only slightly to 12% in 2016 in Western Europe while it shot up to 20% in the United States. Meanwhile, in the United States, the bottom 50% income share decreased from more than 20% in 1980 to 13% in 2016.

At the global level, inequality has risen sharply since 1980, despite strong growth in China.

• The poorest half of the global population has seen its income grow significantly thanks to high growth in Asia (particularly in China and India). However, because of high and rising inequality within countries, the top 1% richest individuals in the world captured twice as much growth as the bottom 50% individuals since 1980. Income growth has been sluggish or even zero for individuals with incomes between the global bottom 50% and top 1% groups. This includes all North American and European lower- and middle-income groups.

• The rise of global inequality has not been steady. While the global top 1% income share increased from 16% in 1980 to 22% in 2000, it declined slightly thereafter to 20%. The income share of the global bottom 50% has oscillated around 9% since 1980 (Figure E5). The trend break after 2000 is due to a reduction in between-country average income inequality, as within-country inequality has continued to increase.

• The rise in wealth inequality has nonetheless been very large in the United States, where the top 1% wealth share rose from 22% in 1980 to 39% in 2014. Most of that increase in inequality was due to the rise of the top 0.1% wealth owners. The increase in top-wealth shares in France and the UK was more moderate over the past forty years, in part due to the dampening effect of the rising housing wealth of the middle class, and a lower level of income inequality than the United States’.

In a future in which “business as usual” continues, global inequality will ­further increase. Alternatively, if in the coming decades all countries follow the moderate inequality trajectory of Europe over the past decades, global income ­inequality can be reduced—in which case there can also be substantial progress in eradicating global poverty.

• Global income inequality will increase if countries prolong the income inequality path they have been on since 1980—even with relatively high income growth predictions in Africa, Latin America, and Asia in the coming three decades. Global income inequality will increase even more if all countries follow the high-inequality trajectory followed by the United States between 1980 and 2016. However, global inequality will decrease moderately if all countries follow the inequality trajectory followed by the EU between 1980 and today

• Within-country inequality dynamics have a tremendous impact on the eradication of global poverty. Depending on which inequality trajectory is followed by countries, the incomes of the bottom half of the world population may vary by factor of two by 2050 (Figure E11), ranging from €4 500 to € 9100 per year, per adult.