Per an old article in Economist Magazine, the value of all outstanding FF miles is greater than the total amount of U.S. dollar currency in circulation, and much greater than any other currency in circulation. This article is from 10 years ago, but we know it has only gotten way worse. Two ytears ago Inside Flier estimated there were 9.7 trillion unredeemed rewards miles given by airlines around the globe. Estimates are that between 25% and 80% of miles are never redeemed. Nice to own a printing press, isn't it?