The human development index (HDI) attempts to make an assessment of 177 very
diverse countries and areas, with very different price levels. To compare
economic statistics across countries, the data must first be converted into a
common currency. Unlike conventional exchange rates, PPP (Purchasing Power
Parity) rates of exchange allow this conversion to take account of price
differences between countries. GDP per capita (PPP
Purchasing Power Parity HDR 2001 [103 KB].