Bubbles have been around for very long time. We all know about the Tulip Bulb Mania and South Sea Bubble, the Roaring Twenties stock market bubble and, more recently, the Tech Bubble that led to the Tech Wreck.

As a general rule, market bubbles were standalone events. What’s different about the current bubble is that it is taking place across a wide range of markets, from houses and commodities to stocks and emerging-market currencies, if not also the currency majors.

Critics argue buyers don’t always use actual dollars as a medium of exchange; they can pay in any convertible currency, just at the dollar price, and thus demand for dollars doesn’t enter into it. Or is the purchase of commodities a hedge against a falling dollar? This is a more complicated story than it appears at first sight, and we will come back to it.