The monthly average crude oil spot prices are calculated from daily quotations. The annual averages are calculated from the average of the twelve months. Prices are either dated (spot price), assessed (based on Platt's weekly assessment of spot prices) or first month forward supply, which is the dated quotation for prompt physical cargoes. Product quality specifications (based on International Crude Oil Market Handbook 2001-2002, Energy Intelligence Group): A blend of crude from the Brent and Ninian systems. Prior to July 1987, the monthly average prices were calculated from the weekly averages from various published sources.
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