The central parity rate of the Chinese currency renminbi, or the yuan, strengthened 25 basis points to 6.6946 against the US dollar Wednesday, according to the China Foreign Exchange Trading System. 
In China's spot foreign exchange market, the yuan is allowed to rise or fall by 2% from the central parity rate each trading day. 
The central parity rate of the yuan against the US dollar is based on a weighted average of prices offered by market makers before the opening of the interbank market each business day.