Gross Domestic Product (GDP) CHINA - 2011
China's GDP is controversial, not least because it's measured differently to other some countries.
The problem lies with the official exchange rate - it's established by government regulation and not determined by market forces - so therefore it's seen as not being a reliable measure of China's output in relation to other countries worldwide.
According to the CIA World Factbook comparisons of output across countries is best judged, in the case of China, by looking at GDP at purchasing power parity - which takes into account the amount of money needed to buy the same goods and services in two different countries and then calculates an implied foreign exchange rate. The IMF estimated China's GDP at purchasing power parity at $11.3tn for 2011.