For a move that had been so long lobbied for and agonised over, China's weekend announcement that it would allow some flexibility back into the value of its currency was greeted by economists with grudging optimism rather than yelps of glee.

Few think the move will have a dramatic impact on the world economy – specifically on the huge global imbalances seen before the financial crisis, which are threatening to re-appear.

Partly, they said, this was because of its limited size. The renminbi offshore forwards market yesterday was predicting an appreciation of just 2.3 per cent by the end of the year. At that rate, very roughly speaking and holding other things equal, it would take China more than a decade to eliminate the currency's overvaluation, estimated to be in the range of 25-40 per.