A world currency, supranational currency, or global currency is a currency that is widely used in international finance or in international trade to price goods or other transactions. It is generally a currency which is stable in terms of inflation and has a high demand on the foreign exchange market. Greek and Roman coins were the first world currency, followed by Dutch guilders in the early 17th century, Spanish dollars through 19th century, and the pound sterling through the early 20th century. The US dollar became the world's principal reserve currency under the Bretton Woods system in 1944. The Bretton Woods gold-convertibility system ended in 1971, and the Jamaica Accords of 1976 formalized the transition to a floating exchange-rate system. The dollar nevertheless remained the dominant global reserve currency and continues to hold that role today.