Sellar and Yateman's book '1066 and All That' was published in 1930. Its last line seemed prescient: "America was thus clearly top nation, and history came to a ."

But history never comes to a full stop. Yes, America has been an economic powerhouse for over 100 years; fuelled by abundant natural resources, manned by a mighty workforce drawn from the four corners of the earth, and aided by the collapse of the iron curtain. But a century is not very long in historical terms.

The question is this: is America still top nation, and if so, for how much longer?

This sort of thinking has come to the fore recently, due to the decline of the dollar. Many currencies are seen as something of a virility symbol, and none more so than the greenback.

In April 2008, the dollar hit its all-time low. It recovered from that abyss since then, but has fallen back again: since March this year it has declined 15 per cent on a trade-weighted index.

Does this matter? For most other currencies, not very much. But the dollar has a special status: the US is the world's largest trading nation and debtor, and the dollar is the world's reserve currency.

Why the decline? Benchmark interest rates are at near zero, while this year's fiscal deficit in the USA is likely to be 10 per cent of GDP (Gross Domestic Product, the value of the goods and services in the economy). Because the dollar is cheap, currency traders can make money by investing them in higher yielding securities, driving the dollar down further.

The only way to stop the decline is for central banks to buy dollars. They have done so, in great quantities, over recent years – and now hold more than makes any kind of economic sense. If they ever decide to stop holding them, the dollar decline could turn into a headlong plummet.

Behind the slightly unreal world of currency trading are some very real facts. The Wall Street Journal's David Malpas, former chief economist of Bear Stearns, points out that US GDP per head is down 25 per cent since 2000. The USA has only just emerged from recession, while China's growth rate is actually increasing: up 7.9 per cent from a year earlier in the second quarter of 2009. It's now the third-largest economy in the world.

Given that China is now the workshop of the planet and has a population of 1.3 billion compared with the USA's 308m, the writing might be on the wall.

Of course, this may take some time. The US economy is still the world's largest, and in GDP terms ($14.4 trillion last year) accounts for a quarter of global GDP.

But the decline of the dollar, the divergence in economic growth rates and the existence of plentiful, cheap labour in other countries suggests that history is still moving on – and that another nation is waiting in the wings for the top spot.