The world economy will consume in the next five years far less oil than previously assumed, the western countries’ energy watchdog said on Friday in a further sign of the impact of the global economic crisis on commodities markets.

The new International Energy Agency forecast came as oil prices on Friday fell to a four-year low of $40.85 a barrel, down more than $2 on the day. Oil prices had suffered their worst week since January 1991, losing more than $12 in five days.