This country is made up of 50 states and linked by a single currency. The same is (largely) true for the European Union. Clearly, there are advantages to having a single currency. Back in 1944 Keynes proposed a single world currency (called "bancor"). His proposal was rejected. Are you generally in favor or against a single "one-world" currency that would replace the dollar, the Euro, the yen, and all the others? Why? Assuming that it is politically possible, how about having the US dollar as the single medium of exchange? After all, internationally, oil is traded in dollars. Or would you favor, for example, gold, silver, or Bitcoins? Why or why not?