The dramatic recent fall of the value of the U.S. dollar grabs headlines every day, even as the U.S. stock market surges to new recovery highs. People are talking about a "dollar crisis," and it's not just the usual rant-and-rave topic on CNBC. There are serious hints from government authorities around the globe that maybe we should think about dethroning the U.S. dollar as the "reserve currency" held by the world's central banks, and maybe global markets like oil should stop being priced in dollars.

There are some currencies that are as weak as the dollar now, such as the British pound. And there are some that are weaker, such as the Malaysian ringgit. But against a basket of the world's major currencies, the dollar has fallen 15% in just seven months. That's a big move in any...