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.
De facto currency De facto currency A de facto currency is a unit of money that is not legal tender in a country but is treated as such by most of the populace. The United States dollar and the European Union euro are the most common de facto currencies. Andorra used the euro unofficially prior to June 2013, at which point the euro became its official currency. The euro remains the de facto currency in Kosovo and Montenegro. Countries using the United States dollar as their de facto currency include Aruba and Cambodia, where most hotels, restaurants, and transportation are priced in dollars;