Euro in Madrid. 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 (US$1.1743). Physical euro coins and banknotes entered into circulation on 1 January 2002, making it the day-to-day operating currency of its original members, and by March 2002 it had completely replaced the former currencies. While the euro dropped subsequently to US$0.83 within two years (26 October 2000), it has traded above the U.S. dollar since the end of 2002, peaking at US$1.60 on 18 July 2008. In late 2009, the
International status and usage of the euro is attractive for international transactions when it demonstrates stability, a well-developed financial market to trade the currency, and acceptability to others. While the euro has made substantial progress, a few challenges undermine the ascension of the euro as a major reserve currency. Persistent excessive budget deficits of some member nations, economically weak new members, conservatism of financial markets, and inertia or path dependence are important factors keeping the euro as a junior international currency to the US dollar. However, at the same time, the USD has increasingly suffered from a double deficit and has its own concerns. As the euro