A lack of investment in the oil industry means a glut of crude is temporary and prices will rebound in the medium to long term, the International Energy Agency’s (IEA’s) chief economist Fatih Birol said.

“We will see downward pressure on the prices in the next few years, but what worries me is that investment is not coming forth, especially in the Middle East,” Birol said at a conference in Prague. “A spike in the oil price has been postponed, but it hasn’t been canceled.”

Prices will climb because demand from developing economies will continue to grow and a lack of investment will limit supply growth when current fields mature, he said. The IEA is an adviser to 29 nations on energy policy. Global demand may grow by 14 MMbbl/d by 2040, he said.

Oil prices have collapsed since OPEC decided to maintain its output target on Nov. 27, prompting speculation that Saudi Arabia and other members want to let North American shale drillers and other producers share the burden of reducing a surplus. OPEC predicted yesterday that global demand for its crude next year will be the weakest since 2003.