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.
Currency substitution financial assets denominated in a foreign currency. It can also occur as a gradual conversion to full currency substitution, for example, Argentina and Peru were both in the process of converting to the U.S. dollar during the 1990s. "Dollarization", when referring to currency substitution, does not necessarily involve use of the United States dollar. The currencies that have been used as substitutes have been the US dollar, the euro, and the Australian dollar. After the gold standard was abandoned at the outbreak of World War I and the Bretton Woods Conference following World War II, some countries sought exchange rate