The Chinese currency Renminbi, or the yuan, retreated to 6.291 against the US dollar on Wednesday, according to the China Foreign Exchange Trading System. In China\'s foreign exchange spot market, the yuan is allowed to rise or fall by 0.5% from the central parity rate each trading day, (Xinhua) News Agency reported . The central parity rate of the yuan against the US dollar is based on a weighted average of prices before the opening of the market each business day.