If you have more than enough of something you expect to fall in value, the answer is to sell. China’s National Bureau of Statistics said on Tuesday the country should speed up the diversification of its foreign exchange reserves. It was unusually explicit that the reason was the risk of a dollar decline. Diversification, however, is a complicated issue.

China’s $941bn of reserves, equivalent to more than 35 per cent of gross domestic product and held largely in dollars, are far larger than needed. Chinese officials also provided details on Tuesday on the appropriate level of reserves – which should be sufficient to finance three months of imports and fully repay overseas debt. In addition, reserves should allow for dividend payments to foreigners, domestic companies investing overseas and for the needs of individuals travelling abroad. But, even on extremely conservative assumptions, only $500bn-$600bn might be required for these purposes.