Why are oil prices staying so high? Blame it on "shortage psychology," said Daniel Yergin, chairman of a consulting firm.

Some speculators think the world is "running out of oil," said Mr. Yergin of Cambridge Energy Research Associates. "As prices go up, this psychology becomes self-reinforcing," he told Congress in a Joint Economic Committee hearing Wednesday.

Thus, fear is driving oil prices ever higher?

"We are in an oil shock," said Mr. Yergin. "Four years ago, oil was around $40 a barrel. Today, it is over $135 a barrel and there are alarming predictions of $200 and $250 a barrel."

Yet there seems to be reason for concern. At the same hearing, the federal Energy Information Administration predicted worldwide demand for energy would increase 50 percent in the next two decades.

China and other developing economies will consume 85 percent more energy by 2030, the agency said.

Mr. Yergin noted that the mortgage crisis, which led to a weaker dollar, also pushed the price of oil up.

The solution? Drive less. Use more renewable energy. Find new oil supplies. Make vehicles more fuel-efficient.

"Prices do not usually go straight up forever," he said. "Markets respond to higher prices with behavioral changes, innovation and substitution, and we are beginning to see that response."