Reserve currency economy, the German Deutsche Mark gained the status of the second most important reserve currency after the US dollar. When the euro was introduced on 1 January 1999, replacing the Mark, French franc and ten other European currencies, it inherited the status of a major reserve currency from the Mark. Since then, its contribution to official reserves has risen continually as banks seek to diversify their reserves, and trade in the eurozone continues to expand. Former U.S. Federal Reserve Chairman Alan Greenspan said in September 2007 that the euro could replace the U.S. dollar as the world's primary reserve currency.
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