Never before have emerging economies been in such a good position to sustain demand during a global downturn. Never before, too, has this been more important for the whole world. But the fact that a line of action is feasible and desirable does not mean it will happen. Optimists believe the emerging economies have decoupled at last. But such optimism may yet prove unhinged.

The cheerful view rests on two propositions: first, the slowdown in US demand will be quite mild; and, second, emerging market economies - and particularly the largest among them - are strong enough to respond effectively. As a result, the world is going to see a passing of the demand baton from the US and, so, benign adjustment of "global imbalances".