Since 1990, poverty analysts have been using the $1 per day standard as the international poverty line for extreme poverty.

More precisely, the extreme poverty standard is set at $1.08, figured in 1993 "purchasing power parity" (PPP) dollars, which allows comparison of poverty rates across countries and across years.

However, most people in rural areas who live in extreme poverty actually survive on significantly less than $1.08 per day. Recent calculations by the World Bank show that the mean income of those living below the poverty line in rural areas throughout the world is just 77 cents.

The difference between this mean income and the poverty line -- 31 cents -- indicates that rural poverty is not only extensive but deep.

SOURCE: Ravallion, R., S. Chen, and P. Sangraula. 2007. New Evidence on the Urbanization of Global Poverty. Summary of World Bank Policy Research Working Paper 4199. Washington, DC: World Bank. 38, 42.