Oil sank to a six-year low Aug. 13 as rising crude output and signs that China’s economy is weakening increased concern that a global surplus will worsen.

Crude closed at the lowest level in more than six years in New York as OPEC production climbed while China’s devaluation of the yuan bolstered concern that the world’s second-biggest economy will slow.

The price of oil fell in New York on May 27 on ample U.S. crude stockpiles as output surged to a record.