No way out

China's trillion dollars in FX reserves is just too big to diversify out of without moving markets. At the moment, "diversification" means leaving it in dollar-denominated assets, but moving away from Treasuries into CMOs or corporates. For now, helping to depress the yield curve on the long end. One popular theory is no big moves before the Beijing Olympics in 2008 (stability is everything). Shout out to Brad Setser :-)

Economist: ...So long as China runs a large external surplus (the natural result of its high saving rate) and refuses to set its currency free, its stash of foreign currency will probably continue to mount.

How that money is invested has big implications for the world economy, not just for China. Brad Setser, head of global research at Roubini Global Economics, estimates that about 70% of it is invested in dollars, mainly Treasury securities. This has propped up the dollar and reduced American bond yields—by up to 1.5 percentage points according to some estimates. A big shift out of dollars could therefore push up bond yields and hence mortgage rates, damaging America's already crumbling housing market.

China's central bank is thought to be switching from Treasury bonds to American mortgage-backed securities and corporate bonds in an attempt to earn higher yields. Chinese officials have also discussed in private the need to diversify reserves out of dollars in order to reduce exposure to a big drop in the greenback. The bank may be putting a bigger slice of any increase in reserves into euros and emerging Asian currencies, but so far there is little sign of a shift out of its existing stock of dollars. One problem is that China's investments are so big that they move markets. Shifting money into euros would push down the dollar. China would then not only suffer a capital loss on its remaining dollar reserves, but it could also be forced to buy yet more reserves to hold its currency down against a weaker dollar.

Fear of a capital loss, and dissatisfaction with unrewarding yields, have triggered a flurry of ideas on how to put the money to better use. One popular idea is to use some of China's reserves to buy oil and other commodities. The snag is that stockpiling oil would push up prices, yet absorb only a tiny proportion of the sums at China's disposal. Buying the equivalent of six-months' oil consumption, as has been suggested, would take only 8% of total reserves at current prices, but the extra oil bought would amount to three times the growth in global oil demand this year. Buying gold would have similar results: if China invested just 5% of its reserves in gold, it could buy the world's entire annual mine production.