The dollar is not just the currency used in the U.S., it is very much the world's currency. It's been that way for 80 years – but that could change. Luis Robayo/AFP via Getty Images hide caption ...

The dollar has been the world’s principal reserve currency since the end of World War II, and is estimated to be used in more than 80 percent of international trade.. Earlier this year ...

While overall demand for US currency is indeed on the rise, with $100 bills outpacing other denominations in both volume and total value, most $100 bills are held abroad. According to the Federal ...