Economically, the USA may reign supreme. However a number of countries - the so-called BRICs - are presenting an increased threat to that level of dominance. In as little as 50 years, predicts Peter Day, the world will be shaped very differently

Think back 50 years. America is in the ascendancy; there is international concern about globalisation (called 'Americanisation' in the 1950s); Europe is taken up with self-definition and a new star rises in the East, in the shape of Japan. In a way, not much has changed.

But look forward 50 years from now, and there are radical upheavals on the way. China and India will duly take their place in the world, with 40% of the world's population now flexing its economic muscles in a proportionate way. And other countries are on the rise, too.

Move over, the current ruling powers. At the very least, the USA and Europe will have to share economic ascendancy with other parts of the world.

And the main changes to the business and economic map of the world will probably involve the rise of the BRICs: Brazil, Russia, India and China. This, anyway, is the fashionable thesis propounded almost two years ago by a team from international investment house Goldman Sachs.

The peculiarly Chinese version of centrally directed Beijing market socialism is driven by the huge migration of people from the country to the cities; this mass movement of people, tens of millions a year for the coming decades, is both the engine for China's growth and the reason it is needed.

India watches China intently and is following slightly behind. But its population is about to outstrip China's and its youth will be a distinct competitive advantage rather than a burden, as China's one-child policy delivers an inevitably ageing workforce.

The Goldman Sachs team estimates that China's economy could be larger than the USA's in 2041, and larger than everyone else's as early as 2016. India may outstrip the size of the - by then shrinking - Japanese economy in 2032.

But, of course, even when China becomes the world's largest economy, it will still be far poorer per head than its economic rivals. So even passing these significant thresholds will not necessarily slow down the momentum of the new economic powers.

Goldman Sachs admits that there are problems in including Russia and Brazil in this view of the world. Brazil has been the coming nation for at least 100 years; Russia's future remains, in the words of Winston Churchill, "a mystery wrapped in an enigma."

Both countries combine big populations with huge resources of raw materials of a kind the world will increasingly need; both countries are already being aggressively courted by China.

But by 2039, there will be a new top table when global leaders meet to discuss economic affairs. That's the year, Goldman Sachs forecasts, when the combined BRICs economies will outstrip the combined size of the Group of Six nations: the USA, Japan, Germany, France, Britain and Italy. At the moment, BRICs make up only 15% of the combined G6 economy now.

But will the existing global leaders move over graciously to allow the newcomers a place in world affairs? If this vision of the future is realised, where and by whom will control be held?

There is nothing particularly magic about the Goldman Sachs analysis; it is based very much on great big populations finally starting to catch up with the developed world in terms of wealth. But it surely means a severe jolt to our received idea of what the world is and how it works.

Growing up in Britain in the 1950s, 'made in Japan' meant cheap and nasty, yet within 20 years the picture of Japanese exports was entirely changed. China is halfway into the transformation already, and India is close behind.