The Chinese currency Renminbi, or the yuan, weakened 22 basis points to 6.3235 against the U.S. dollar on Thursday, according to the China Foreign Exchange Trading System. The retreat marks the fourth straight day of decline against the U.S. dollar. The yuan hit 6.2919 against the U.S. dollar on Feb. 29, a record high since the country started reforming its exchange rate formation mechanism in 2005. In China\'s foreign exchange spot market, the yuan is allowed to rise or fall by 0.5 percent from the central parity rate each trading day. The central parity rate of the yuan against the U.S. dollar is based on a weighted average of prices before the opening of the market each business day.