"Its GDP per capita is $900 compared to the US $35,200."
China
http://www.odci.gov/cia/publications/factbook/geos/ch.html
Population: 1,298,847,624 (July 2004 est.)
GDP: $6.449 trillion (2003 est.)
GDP per capita: $4965
United States
http://www.odci.gov/cia/publications/factbook/geos/us.html
Population: 293,027,571 (July 2004 est.)
GDP: $10.99 trillion (2003 est.)
GDP per capita: $37505
The CIA explanation: In the Economy category, GDP dollar estimates for all countries are derived from purchasing power parity (PPP) calculations rather than from conversions at official currency exchange rates. The PPP method involves the use of standardized international dollar price weights, which are applied to the quantities of final goods and services produced in a given economy. The data derived from the PPP method provide the best available starting point for comparisons of economic strength and well-being between countries. The division of a GDP estimate in domestic currency by the corresponding PPP estimate in dollars gives the PPP conversion rate. Whereas PPP estimates for OECD countries are quite reliable, PPP estimates for developing countries are often rough approximations. Most of the GDP estimates are based on extrapolation of PPP numbers published by the UN International Comparison Program (UNICP) and by Professors Robert Summers and Alan Heston of the University of Pennsylvania and their colleagues. In contrast, the currency exchange rate method involves a variety of international and domestic financial forces that often have little relation to domestic output. In developing countries with weak currencies the exchange rate estimate of GDP in dollars is typically one-fourth to one-half the PPP estimate.