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
Currency swap currency exchange have since become rare, savings are still available from back-to-back loans due to comparative advantage. The first formal currency swap, as opposed to the then used parallel loans structure, was transacted by Citicorp International Bank for a $US100,000,000 10 year US Dollar Sterling swap between Mobil Oil Corporation and General Electric Corporation Ltd (UK). The concept of the interest rate swap was developed by the Citicorp International Swap unit but cross-currency interest rate swaps were introduced by the World Bank in 1981 to obtain Swiss francs and German marks by exchanging cash flows with IBM. This deal was