Because of the different demand/supply balance in each region and the cost of transporting the oil between regions, a tanker of Brent crude oil in the UK will have a different value to a UK buyer than a tanker of Arab light crude oil in Singapore, which results in the basis risk.

Calendar spreads represent a special case of basis risk and occur when the relative prices of commodity futures do not come in alignment and the trader becomes exposed to the absolute price movements.

In most commodities, the longest term contracts are the most volatile, while the shortest term forward contract are the least volatile.

Some commodities can be both in backwardation and a have a strong seasonal element.