" The first cut at the problem—the simplest but still eye-opening—is to ask how much income would have to be transferred from rich countries to poor countries to lift all of the world’s extreme poor to an income level sufficient to meet basic needs. Martin Ravallion and his colleagues on the World Bank’s poverty team have gathered data to address this question, at least approximately. The World Bank estimates that meeting basic needs requires $1.08 per day per person, measured in 1993 purchasing-power adjusted prices. Using household surveys, the Ravallion team has calculated the numbers of poor people around the world who live below that threshold, and the average incomes of those poor. According to the Bank’s estimates, 1.1 billion people lived below the $1.08 level as of 2001, with an average income of $0.77 per day, or $281 per year. More important, the poor had a shortfall relative to basic needs of $0.31 per day ($1.08 minus $0.77), or $113 per year. Worldwide, the total income shortfall of the poor in 2001 was therefore $113 per year per person multiplied by 1.1 billion people, or $124 billion. Using the same accounting units (1993 purchasing power adjusted U.S. dollars), the income of the twenty-two donor countries of the Development Assistance Committee (DAC) in 2001 was $20.2 trillion. Thus a transfer of 0.6 percent of donor income, amounting to $124 billion, would in theory raise all 1.1 billion of the world’s extreme poor to the basic-needs level. Notably, this transfer could be accomplished within the 0.7 percent of the GNP target of the donor countries. That transfer would not have been possible in 1980, when the numbers of the extreme poor were larger (1.5 billion) and the incomes of the rich countries considerably smaller. Back in 1981, the total income gap was around $208 billion (again, measured in 1993 purchasing power prices) and the combined donor country GNP was $13.2 trillion. Then it would have required 1.6 percent of donor income in transfers to raise the extreme poor to the basic-needs level. "
― Jeffrey D. Sachs , The End of Poverty