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
S-train expansion and new trains). Plans for further extension of system include another two lines, one of which should reach Belgrade Nikola Tesla Airport. "S-Bahn" is also used in German-speaking Switzerland. While French publications of those networks translate it as "RER", the line numbers are still prefixed with an S (e.g. S2). The oldest network in Switzerland is the Bern S-Bahn, established in stages from 1974 and has adopted the term S-Bahn since 1995. It is also the only one in Switzerland to use a coloured "S" logo. In 1990, the Zürich S-Bahn, which covers the largest area, went into service.