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
World currency or "supercurrency", as the proposed terra or the DEY (acronym for Dollar Euro Yen), produced and supported by a central bank which is used for "all" transactions around the world, regardless of the nationality of the entities (individuals, corporations, governments, or other organizations) involved in the transaction. No such official currency currently exists. Advocates, notably Keynes, of a global currency often argue that such a currency would not suffer from inflation, which, in extreme cases, has had disastrous effects for economies. In addition, many argue that a single global currency would make conducting international business more efficient and would encourage