Historians have tried to estimate the extreme poverty rate in 1820 using different methods, and their results differ widely. Gapminder roughly estimates that 85 percent of the world population lived on Level 1 in 1800. The post-1980 data comes from PovcalNet. Gapminder has extended the trend to 2017 using PovcalNet and IMF forecasts. The numbers in the text on the reductions in extreme poverty in China, India, Latin America, and elsewhere come from World Bank.
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