"Prevailing measures of relative poverty put an implausibly high weight on relative deprivation, such that measured poverty does not fall when all incomes grow at the same rate. This stems from the (implicit) assumption in past measures that very poor people incur a negligible cost of social...

The authors present new estimates of the extent of the developing world's progress against poverty. By the frugal $1 a day standard, they find that there were 1.1 billion poor in 2001-almost 400 million fewer than 20 years earlier. Over the same period, the number of poor declined by more than...