America’s poverty line is $63 a day for a family of four. In the richer parts of the emerging world $4 a day is the poverty barrier. But poverty’s scourge is fiercest below $1.25 (the average of the 15 poorest countries’ own poverty lines, measured in 2005 dollars and adjusted for differences in purchasing power): people below that level live lives that are poor, nasty, brutish and short.
Source: wiktionary