Currency intervention is the buying or selling of currency by central banks in an attempt to manipulate the price of a particular currency.a consumer in the U.S. buys a Chinese product, Chinese manufacturers are paid in US dollars. These U.S. dollars are then deposited in a U.S. bank account. At this point, the Chinese exporter needs to convert dollars into yuan. Through its commercial bank it sells the U.S. dollars to the Chinese central bank, the People's Bank of China. Since the trade between the United States and China does not balance, there is a shortage of yuan and a surplus of U.S. dollars in the Chinese central bank. The usual remedy to this situation used in international trade would be for the Chinese central bank sell its dollars on international currency markets and buy yuan in exchange, resulting in a self-correcting system: the U.S. dollar weakens and the Chinese yuan strengthens, until equilibrium is restored and the trade gap closes.It slows the appreciation of the Yuan, or in some cases effectively pegs the CNY against the USD. The central bank net buys USD, then sterilizes the excess dollar flows by buying dollar-denominated assets, such as U.S. treasuries. This has the effect of keeping the excess dollars out of the currency exchange markets, where they would cause a correction in the exchange rates. Thus, the Chinese central bank manipulates the exchange rates by creating yuan and buying U.S. debt. This "printing" of Chinese Yuan by the central bank is not without consequence, however, since in excess if yuan are created faster than domestic economic output) it would eventually lead to inflation, causing consumer prices to rise. Economist Paul Krugman writes that by keeping its currency artificially weak China generates a dollar surplus.