Why are oil prices so stubbornly high?

The Arab Spring caused oil prices to surge above $100 a barrel, but much of the violence has now passed and exporters like Libya are again turning on the taps.

One might expect the price of oil to drop, but Brent crude is still trading near $111 a barrel despite fears the world could slip into another recession.

So why is the price of oil so stubbornly high?

Philip Hampsheir reports.