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.
Andorra and the euro facto" used the EU's euro (the currency of the Eurozone states) as it had historically used the French franc and Spanish peseta. When those two currencies were replaced by the euro in 2002, the euro replaced the franc and peseta as the sole circulating currency in Andorra. Unlike the three other European microstates outside of the EU, Monaco, San Marino and the Vatican City, which adopted the euro when it was introduced, Andorra did not conclude a monetary agreement with the EU but rather used it unilaterally. These agreements gave the three microstates the right to issue their own euro