Please visit GiveWell.org This CharityScorecard.org site was in use from 2006 to 2008, but is now mostly dormant, and the material here is out of date. The GiveWell project has similar goals and is being actively maintained. I've left the old CharityScorecard.org content here just for the historical record.

From CharityScorecard

Purchasing power parity (PPP) 

A hypothetical exchange rate or conversion factor between currencies in different countries, used for adjusting GDP per capita figures to account for differences in cost of living. Local prices are expressed in Int$ after doing a purchasing power parity converstion. See also: http://en.wikipedia.org/wiki/Purchasing_power_parity

• See also: World Bank list of PPP conversion factors by country