Reserve currency before the beginning of the worldwide credit crunch related recession and Eurozone crisis, which harmed the euro and slowed its adoption. Since 2009, the reserve currency use of the euro has continued to drop, down to 23.9 percent in 2013. The Dutch guilder was the "de facto" reserve currency in Europe in 17th and 18th centuries. The United Kingdom's pound sterling was the primary reserve currency of much of the world in the 19th century and first half of the 20th century. The emergence of the USA as an economic superpower, and the establishment of the U.S. Federal Reserve System
Non-decimal currency Non-decimal currency A non-decimal currency is a currency that has sub-units that are a non-decimal fraction of the main unit, i.e. the number of sub-units in a main unit is not a power of 10. Today only two countries in the world use non-decimal currencies. Both of these countries are in Africa. These are Mauritania (1 ouguiya = 5 khoums) and Madagascar (1 ariary = 5 iraimbilanja). However these are only theoretically non-decimal, as in both cases the value of the main unit is so low that the sub-unit is too small to be of any practical use and coins