The behaviour of the oil and commodities markets in the past two years provides a fascinating natural experiment for economists. The price of oil has roughly tripled since early 1999, to stand at more than $33 (€38.37) a barrel early this week, while non-oil commodities have barely risen at all.

The divergence may settle at last the long-running dispute over whether a rise in the price of oil must necessarily plunge the world into another recession.

Oil's effect on headline consumer price inflation so far is obvious. US inflation has hit an annual rate of 3.5 per cent, while the underlying rate excluding food and energy is 2.6 per cent. Euro-zone inflation has hit 2.8 per cent, while the rate excluding oil and other volatile components is 1.4 per cent.

Economists are in agreement that this is not the real issue. The important question is whether there will be a return to the combination of recession and inflation characteristic of the 1970s. Where they differ is over how far that stagflation can be blamed on the price of a single commodity.

One explanation of the global economic catastrophe of the 1970s lays the blame squarely at the door of the Organisation of Petroleum Exporting Countries (OPEC).

The oil price surge of 1973, it is argued, sucked wealth from oil-consuming countries, hurt productivity by distorting production costs and set off a wage-price spiral. It was certainly the trigger, if not the sole cause, of the collapse of the great post-Second World War boom.

A rival view says the cause was broader economic failure, set off by the surge in public spending in the US to pay for the Vietnam War and Lyndon Johnson's Great Society programme, by the breakdown of the global system of fixed exchange rates, and by the US Federal Reserve's decision to hold interest rates down in 1971-72.

This view sees the oil price rise of 1973 as a symptom, rather than a cause, of a global boom that inevitably went bust. And it points to a coincidental surge in prices of most other commodities as evidence that strong worldwide demand, not OPEC's supply controls, were the most important feature of the early 1970s. Scrap metal and lumber prices took off in 1971-72, for example.

Until now the argument has been impossible to resolve, because non-oil commodities have tended to follow the movements in the price of oil quite closely. But in the past year non-oil commodities have risen by 2 per cent. Agricultural commodities are down 6 per cent, while industrial materials are up 15 per cent. For the first time, it may be possible to isolate the significance of oil.

Prof Andrew Oswald of Warwick University, England, believes it is all-important. "Oil is unique because it has a monopoly position in transport," he says.

"Oil has never risen as much as it has done since 1999 without triggering a global recession."

Economists who play down the significance of oil, on the other hand, are quite sanguine. "We do not believe that there is any reason for stagflation to reignite at this point," says Mr Lutz Kilian of the University of Michigan in the US. There have been a few second-round price effects in the US and elsewhere. Air fares and some delivery rates have gone up. The price of beer has risen because of higher transport costs in the US. But, crucially, inflation expectations have stayed low: the US public expects the oil-driven spike to be temporary.

Prof Oswald admits there is not much evidence of the world economy plunging into recession. In fact, the International Monetary Fund recently proclaimed the best economic outlook for a decade.

But he suggests that the slowdown in US growth in the third quarter may be a harbinger of the storm to come. "Hard landings always look like soft landings at the beginning," he says. In the meantime, the structural changes across the developed world, including privatisation, deregulation and the weakening of trade unions, are reasons for optimism.

As Paul Donovan of UBS Warburg puts it: "The rise in the oil price is not a cause to panic. In the 1970s, they had a wage-price spiral because they had rigid labour markets, but that was a very different economy to this one."

With global oil output exceeding consumption by about a million barrels per day, analysts are predicting the price may begin to fall back quite quickly once the winter is over.

This may turn out to be the first oil shock that the world economy manages to survive.