One of the most famous measures of absolute or extreme poverty is indeed the dollar a day. When this level was set by World Bank economists in 1990, it matched closely to the poverty line in many poor countries - in other words, the basic income people needed in order to survive. But the dollar a day was also picked because it was simple and striking: “We intended to have some impact with it,” Martin Ravallion, an economist who was formerly at the World Bank, told the BBC. “