The euro is the second largest reserve currency as well as the second most traded currency in the world after the United States dollar. As of July 2011, with nearly €890 billion in circulation, the euro has the highest combined value of banknotes and coins in circulation in the world, having surpassed the U.S. dollar. Based on International Monetary Fund estimates of 2008 GDP and purchasing power parity among the various currencies, the eurozone is the second largest economy in the world. The name euro was officially adopted on 16 December 1995. The euro was introduced to world financial markets as an accounting currency on 1 January 1999, replacing the former European Currency Unit (ECU) at a ratio of 1:1. Euro coins and banknotes entered circulation on 1 January 2002.