Highest-price scenario

The global economy recovers more quickly than expected, driving higher oil demand. A war in the Gulf wipes out Iraqi production capacity and leaves the region unstable. The Venezuelan crisis persists, keeping upward pressure on prices. Non-OPEC production growth slows. 2003 average price: $30+ a barrel

Lowest-price scenario

A second economic dip in the US and European economies leads to a contraction in oil demand, while non-OPEC production increases by 1 million b/d. War in the Gulf is averted and sanctions on Iraq are lifted. In Venezuela, President Chavez is overthrown and the new regime pumps cash into new oil capacity. OPEC discipline disintegrates. 2003 average price: $15 a barrel

Probable scenario

The global economy remains sluggish, keeping oil demand growth low. Non-OPEC production grows. UN action in Iraq drives prices up to around $30 a barrel, which are sustained for up to two months. Chavez remains in power but makes concessions to the opposition, including higher oil production and more money for PDV. OPEC members overproduce by around 5 per cent. 2003 price average: $23 a barrel

OPEC’s most-favourable scenario

The global economy recovers faster than expected, increasing oil demand. Non-OPEC production grows more slowly than expected. War in the Gulf is averted, but tension remains high. Chavez faces off his opponents and renews quota discipline. The higher prices allow OPEC to overlook some quota cheating by its needier members. 2003 price average: $26 a barrel