Currency War of 2009–11 dollar, with Goldman Sachs saying the real is the most over valued currency in the world. In October 2010, Brazil began increasing her capital controls, doubling a tax on foreign purchases of fixed-income assets to 4 percent so as to curb the real's appreciation to a two-year. On 18 October, Brazil sought to curb the real's gains by raising taxed capital inflow on fixed-income assets by 2% to 6% and taxed inflows for margin deposits on futures to 6% from 0.38%. Chile said it would implement capital controls to curb gains in the Chilean peso, which had strengthened the most
World currency a single world currency is unnecessary, because the U.S. dollar is providing many of the benefits of a world currency while avoiding some of the costs. If the world does not form an optimum currency area, then it would be economically inefficient for the world to share one currency. In the present world, nations are not able to work together closely enough to be able to produce and support a common currency. There has to be a high level of trust between different countries before a true world currency could be created. A world currency might even undermine national sovereignty