No, having different currencies keeps some measure of economic independence If every country had the same currency, then problems affecting the currency in one area of the world would be felt world-wide. Just take a look at what is happening in Europe - the fact that Greece is having economic troubles is causing problems for everyone in Europe, even in countries with stable economies. In addition, one of the reasons that the US dollar is so stable is that it has the full faith and credit of the U.S. government behind it. What entity would stand behind a world currency that would allow everyone to have confidence in it? It would require a vastly different governing structure, to be sure!