THIS week revised figures revealed that China overtook Germany in 2007 to become the world’s third-biggest economy. At the start of last year China also looked set to become the world’s biggest exporter, but a slump in exports in the final months of the year meant they remained smaller than Germany’s. China’s exports tumbled by 13% (in dollar terms) in the fourth quarter, leaving them 3% lower in December than a year earlier. Despite this, China’s trade surplus rose to a record $457 billion at an annual rate in the fourth quarter—50% bigger than in the same period of 2007. What is going on? 

In the first half of 2008 China’s trade surplus did indeed shrink (see chart). But since then, although exports slumped, imports fell by much more—down by 21% in the 12 months to December. The slide in both exports and imports was exacerbated by the global credit freeze, which has made it harder for companies around the world to get letters of credit to guarantee payment. Imports were also dragged down by cheaper oil and commodity prices, and by weaker imports of materials and components used to make exports (over 50% of total imports).

But a more worrying reason why China bought less from the rest of the world is that its domestic demand has weakened. Consumer spending and manufacturing investment have so far held up reasonably well, but construction—a big user of imported raw materials—has collapsed.

With most of the world in recession, China’s exports will continue to slide this year. Nomura forecasts a drop of 6%—the first annual decline for more than 25 years. Imports, on the other hand, are expected to increase. By mid-year, the government’s planned massive increase in infrastructure spending will boost imports of raw materials and machinery. If so, China’s trade surplus will shrink in 2009.

The collapse in exports and the consequent job losses in southern China have triggered speculation that the government might try to push down the value of the yuan. But not only would this provoke a protectionist backlash from America’s new government, it would also do little to help producers. China’s problem is weak foreign demand, not competitiveness. The best way for China to support its economy—and to help unwind global trade imbalances—is to bolster domestic demand.

One piece of good news this week is that, following interest-rate cuts and the government’s scrapping of credit restrictions, total bank loans jumped by 19% in the 12 months to December, up from growth of 14% last summer. China is perhaps the only big economy where credit growth has heated up in recent months. If that is sustained, it could help to boost domestic spending.

China certainly cannot rely on exports any more. Becoming the world’s biggest exporter will be of little comfort if global trade is spiralling downwards.