"The Americans get the toys, the Chinese get the Treasuries and we get screwed." Thus a European Union official once characterised the pattern of Beijing accumulating US assets by selling renminbis for dollars, while nothing stood in the way of a rapid and destabilising appreciation of the euro.

It was this routine that led to the US running a huge current account deficit with counterpart surpluses in much of east Asia (including China) and parts of Europe, and among the oil exporters of the Middle East. A shift in exchange rates is almost certainly a necessary part of rebalancing the world economy, shifting the burden of consumption towards those surplus areas - a task that Ben Bernanke, Federal Reserve chairman, recently called "extraordinarily urgent".