How do you spend $1,810bn? That is the question facing China's State Administration of Foreign Exchange. The world's largest investment fund, it has grown by $400bn this year alone. Having reserves far in excess of what it needed for insurance and currency interventions, it rightly decided to diversify and set up the China Investment Corporation, the country's $200bn sovereign wealth fund. As the Financial Times reveals today, however, Safe itself has been investing abroad. Its foreign equity positions are greater than those of CIC. This raises questions for the developed world and China.

Safe is more secretive and has far deeper pockets than CIC. Given its rapid rate of growth, it may soon be larger than every other nationally owned fund put together. But, although it has been painfully reticent, Safe only seems to have bought small slices of western companies so far. Moreover, there is no suggestion that it has invested in anything of great sensitivity or strategic importance.

Safe's dealings with Costa Rica do, however, demonstrate potential dangers. These show that it is ready to invest as a means of applying political pressure. They are also a demonstration of the great lengths to which Safe is willing to go in order to hide its positions. It is an opaque institution, without open oversight of its assets or objectives.