Economical difficulties

Some economists argue that a single world currency is unnecessary, because the U.S. dollar already provides 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.A world currency would not allow for adjustments by national central banks to accommodate local economic problems. A single currency can only have a single interest rate. However, different regions in the world, with varying rates of economic growth, may require different interest rates