Most economists agree they have no idea whether this second round of quantitative easing will work. That the $600bn programme announced on Wednesday was in line with expectations at least had none of them looking stupid – for now.

Investors, on the other hand, reckon they have it all worked out. QE2 is great for equities (the S&P?500 is up 5 per cent since Federal Reserve chairman Ben Bernanke gave a strong hint that more was coming), bonds (lower yields is the point, right?) as well as real assets from cotton to gold (expanding the monetary base equals higher prices, perhaps even runaway inflation).

Investors – burnt twice since 2000 – should show a little humility. This near-ubiquitous view could well be wrong. Take bonds. As Smithers?&?Co points out, buying bonds while spurring inflation raises the price of bonds while lowering their real value– the definition of a bubble. And bonds look ludicrously overvalued already: for long-dated Treasuries to match their historic real annual return of 3 per cent requires inflation to average less than 1 per cent for the next 30 years.