<P> Economists debate whether a single reserve currency will always dominate the global economy . Many have recently argued that one currency will almost always dominate due to network externalities (sometimes called "the network effect"), especially in the field of invoicing trade and denominating foreign debt securities, meaning that there are strong incentives to conform to the choice that dominates the marketplace . The argument is that, in the absence of sufficiently large shocks, a currency that dominates the marketplace will not lose much ground to challengers . </P> <P> However, some economists, such as Barry Eichengreen, argue that this is not as true when it comes to the denomination of official reserves because the network externalities are not strong . As long as the currency's market is sufficiently liquid, the benefits of reserve diversification are strong, as it insures against large capital losses . The implication is that the world may well soon begin to move away from a financial system dominated uniquely by the US dollar . In the first half of the 20th century multiple currencies did share the status as primary reserve currencies . Although the British Sterling was the largest currency, both the French franc and the German mark shared large portions of the market until the First World War, after which the mark was replaced by the dollar . Since the Second World War, the dollar has dominated official reserves, but this is likely a reflection of the unusual domination of the American economy during this period, as well as official discouragement of reserve status from the potential rivals, Germany and Japan . </P> <P> The top reserve currency is generally selected by the banking community for the strength and stability of the economy in which it is used . Thus, as a currency becomes less stable, or its economy becomes less dominant, bankers may over time abandon it for a currency issued by a larger or more stable economy . This can take a relatively long time, as recognition is important in determining a reserve currency . For example, it took many years after the United States overtook the United Kingdom as the world's largest economy before the dollar overtook the pound sterling as the dominant global reserve currency . In 1944, when the US dollar was chosen as the world reference currency at Bretton Woods, it was only the second currency in global reserves . </P> <P> The G8 also frequently issues public statements as to exchange rates . In the past due to the Plaza Accord, its predecessor bodies could directly manipulate rates to reverse large trade deficits . </P>

When did the dollar become the reserve currency