The oil revenues of member states belonging to international cartel Opec will fall 42 per cent in 2009 because of lower oil production and lower prices, according to the US’ Energy Information Administration (EIA).

The 12 Opec countries will earn $559bn in 2009, down from $971bn they made in 2008, says the agency. This figure is based on its 2009 forecasts for average production and average oil prices.

The EIA forecasts that Opec members’ oil revenues will total $675bn in 2010, on the same basis.

Opec accounts for 33 per cent of world oil production and 85 per cent of spare oil production capacity.

In December 2008, the organisation voted to cut its production by 4.2 million barrels a day (b/d) from September 2008 levels, to 24.9 million b/d.

The average price for Opec crude oil was $94 a barrel in 2008. The average price up until September 2009 is $55.9 a barrel.