S7 Ep29: What the $1-a-day global poverty line gets wrong

It's 1990. A young staff economist walks into a director's office at the World Bank and says the number he's about to publish is "crazy". The director tells him not to worry about it. 

The number was the dollar-a-day poverty line. Lant Pritchett, now of LSE, was that economist. More than three decades later, he's still worrying about it. In this week’s episode he argues that the dollar-a-day line warped how the world thinks about poverty, by setting the bar so low that we can count billions of deprived people as not poor.

In a new paper, co-authored with Martina Viarengo (Graduate Institute, Geneva), their fix isn't to scrap the low line. It's to add a high one as well. They propose a global upper-bound poverty line of $21.50 a day, ten times the extreme-poverty standard, derived from four separate measures of material wellbeing.

Above it, you're no longer poor by any reasonable global standard. Below it, you're poor in a sense worth measuring. By that standard, 99% of Pakistan is poor, and almost no one in Denmark is. Should that affect how we think about anti-poverty policy? 

The research behind this episode:

Pritchett, Lant, and Martina Viarengo. Forthcoming. "Raising the Bar: An Inclusive Global Poverty Line." Journal of Development Economics. Available now as a working paper.

To cite this episode:

Phillips, Tim, and Lant Pritchett. 2026. "What the $1-a-day global poverty line gets wrong." VoxDev Talks (podcast). 

Assign this as extra listening. The citation above is formatted and ready for a reading list or VLE.

About the guest

Lant Pritchett is a development economist and Visiting Professor at the School of Public Policy at the London School of Economics. He worked at the World Bank from 1988 to 2007 and taught at the Harvard Kennedy School for nearly two decades. His work spans economic growth, state capability, education systems, and labour mobility.

The paper is co-authored with Martina Viarengo, Professor of International Economics at the Geneva Graduate Institute. Her research spans public policy, labour markets, comparative education, and international migration.

Research cited in this episode

The dollar-a-day poverty line. Created for the World Bank's 1990 World Development Report on poverty and based on the observation that national poverty lines in the poorest countries clustered at a low floor (Ravallion, Datt and van de Walle 1991). Updated for inflation, it now sits at P$2.15 a day in 2017 purchasing power parity. It was only ever meant to mark the lowest a global poverty line could plausibly be, not the line.

The focus axiom. A standard property of poverty measures, originating with Amartya Sen (1976), under which changes in the income of anyone above the poverty line do not register in the measure. Pritchett's objection is that this assigns mathematically zero weight to the near-poor; a household just above the line counts the same as a Danish millionaire, namely zero. He calls it an economic bug that became a political feature, because it takes global redistribution off the table.

Gresham's law applied to poverty. Pritchett's framing for how the simple headcount displaced richer, distribution-sensitive approaches; bad economics drove out better economics because it was easier to understand. He notes the World Bank of the 1970s was preoccupied with distribution, citing Hollis Chenery and Montek Ahluwalia's Redistribution with Growth (1974), so the idea that economists ignored distribution until poverty measurement arrived is a myth.

The two criteria for an upper bound. The proposed line rests on two ideas drawn from the tension between the focus axiom and standard welfare economics. One, material wellbeing achievement; the line sits where a household reaches a standard of living a rich-country citizen would recognise as adequate. Two, near enough satiation; the line sits where the extra wellbeing from another dollar has fallen so low that treating further gains as zero does little violence to reality. At twenty-one and a half dollars the marginal utility of income is roughly three percent of its value at the dollar-a-day line; at the World Bank's current high line of P$6.85 it is still around thirty percent.

Four measures of wellbeing. The number is triangulated across an iso-elastic utility function, food shares in consumption (Engel's Law), a household index of six basic conditions drawn from Demographic and Health Survey data, and a cross-national index of basics. The estimates cluster between twenty and forty dollars a day; twenty-one and a half was chosen because it is exactly ten times the dollar-a-day line, a focal point in the same way one dollar was.

The six minimal conditions of prosperity. Electricity, improved sanitation, safe water, primary schooling completed by older children, no child dying under five, and no young child malnourished. The test Pritchett applies is whether it would be absurd to call a household prosperous while it lacks one of them.

The rich of the poor and the poor of the rich. The tenth percentile in Denmark has higher consumption than the ninetieth percentile in Pakistan or Indonesia. This is why any global line that produces meaningful poverty in rich countries implies poverty rates near one hundred percent across most of the developing world; a point Dani Rodrik (2007) showed is widely misunderstood.

The prosperity gap. A distribution-sensitive welfare measure adopted by the World Bank (Kraay et al. 2025) that weights the whole income distribution rather than counting everyone above a threshold as zero. Pritchett offers it, alongside poverty-gap and squared-poverty-gap measures at a higher line, as the practical route to acting on a global upper bound without reducing everything to a single headcount.

More VoxDev Talks episodes

Rethinking evidence and refocusing on growth in development economics, Lant Pritchett on what the problem might be if we rely exclusively on rigorous evidence in development economics as a guide for policy.

Rethinking how we measure extreme poverty, Charles Kenny asks: is it time for a new measure of extreme poverty?