The US is likely to start growing over the next few quarters. But US households are likely to remain subdued, as they cope with high debt and the prospect of unemployment. As the fiscal stimulus wears off, and the massive buildup of US government debt limits spending, the world will look elsewhere for demand growth.

The obvious candidates are the emerging markets. But they would have to change strategy, from pushing exports to expanding domestic demand. For countries like China, this would bring a welcome rebalancing of growth, from red-hot coastal areas to more remote western provinces. It would reduce regional inequality and the accompanying political tensions.

But something more dramatic could happen in the longer run when emerging market demand grows. Today, over three-quarters of the value added in a $200 Apple iPod consists of services such as design, marketing, advertising and finance, which are provided by firms in developed countries that are close to today's consumer. Less than a quarter of the value added comes from the manufacturing and assembly, typically done in an emerging market. But when emerging market consumers account for a greater share of world spending, companies closer to them will be better able to anticipate their needs and innovate, design and market to their tastes.