THE world's largest developing countries are questioning the US dollar's supremacy in the international monetary system, and look to the day when it will be replaced by the euro, yen or yuan, or a new international currency. The greenback replaced gold as the measuring standard in the 1970s when central banks started floating their currencies. It had already become a key part of international trade in the early 20th century, replacing the British pound.

$US hard to dislodge as world's reserve currency