FACTBOX: Why oil prices are at a record high

(Reuters) - U.S. crude oil hit an all-time high of $122 a barrel on Tuesday.

Robust demand for crude and a weak dollar have fuelled the rally from a dip below $50 at the start of 2007.

Adjusted for inflation, oil is now above the $101.70 peak hit in April 1980, according to the International Energy Agency, a year after the Iranian revolution.

DOLLAR WEAKNESS

The fall in the value of the dollar against other major currencies has helped drive buying across commodities as investors view dollar assets as relatively cheap.

It has also reduced the purchasing power of OPEC's revenues and increased the purchasing power of some non-dollar consumers.

OPEC oil ministers have noted that although prices are rising to record nominal levels, inflation and the dollar have softened the impact.

Some analysts say investors have been using oil as a hedge against the weaker dollar.

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