How Economists Built the World's Extreme Poverty Line
In 1990, World Bank researchers sought a single, objective benchmark to measure extreme global deprivation. Examining national poverty thresholds across the world's poorest nations, they discovered that local lines clustered around roughly $31 a month—about one dollar a day. Adjusted periodically for global inflation and purchasing power, this benchmark was updated to $1.90 in 2015 and $2.15 in 2022, providing the foundation for monitoring global progress against severe poverty.
The Search for a Common Denominator
Before the early 1990s, measuring poverty across the globe was an exercise in comparing fundamentally incompatible numbers. Every country established its own domestic poverty line based on local priorities, dietary habits, and political considerations. A family considered poor in a high-income nation might have access to running water, public schooling, and modest social assistance, while a household living at the official poverty threshold in a low-income nation struggled to secure daily caloric intake. Because national definitions varied so wildly, international organizations could not determine whether global poverty was rising or falling, nor could they fairly allocate international aid.
In 1990, researchers at the World Bank set out to construct a single, objective benchmark for extreme global deprivation. Rather than inventing an arbitrary number, they looked directly at how the world's poorest nations defined poverty for themselves. Gathering national poverty lines from dozens of low-income countries, the researchers compiled and compared the data. They discovered a striking pattern: across the poorest economies, the national lines did not fall in random scatterplots, but clustered consistently around approximately $31 per month, or roughly one dollar per day.
This shared standard formed the conceptual basis of the international poverty line. It defined extreme poverty not as relative deprivation compared to wealthy neighbors, but as absolute deprivation—the bare minimum required to satisfy basic nutritional and non-food necessities for human survival. Anyone living below this threshold was facing an emergency level of deprivation, regardless of where on Earth they resided.