Purchasing power parity exchange rates for the global poor

The first of the Millennium Development Goals targets global poverty. The numbers that support this goal are estimated by the World Bank, and come from a worldwide count of people who live below a common international poverty line. This line, loosely referred to as the dollar-a-day line, is calculated as an average over the world's poorest countries of their national poverty lines expressed in international dollars. The counts of those living below the line come from household surveys, the number and coverage of which have steadily increased over the years. National poverty lines are converted to international currency using the purchasing power parity (PPP) exchange rates from the various rounds of the International Comparison Program (ICP). These PPPs, unlike market exchange rates, are constructed as price indexes that compare the level of consumer prices across countries.