The extreme volatility that has gripped oil markets for the past 18 months has shown no signs of slowing down, with oil prices more than doubling since the beginning of the year despite an exceptionally weak economy.

The instability of oil and gas prices is puzzling government officials and policy analysts, who say it could jeopardize a global recovery. It is also hobbling businesses and consumers, who are already facing the effects of a stinging recession, as they try in vain to guess where prices will be a year from now — or even next month.

The past 12 months have seen a wild run on the oil markets. Last summer, prices surged to a record high above $145 a barrel, driving up gasoline prices to well over $4 a gallon. As the global economy collapsed, oil tumbled to $33 a barrel in December. But oil has risen 55 percent since the beginning of the year, pushing gas prices up again to a new national average of $2.611 a gallon, according to the Oil Price Information Service and AAA, the automobile club. Crude for August delivery fell $2.68 Monday to $64.05 a barrel on the New York Mercantile Exchange. It was the fourth straight day of declines since hitting a midday high for the year last Tuesday.

“To call this extreme volatility might be an understatement,” said Laura Wright, the chief financial officer at Southwest Airlines, a company that has sought to insure itself against volatile prices by buying long-term oil contracts. “Over the past 15 to 18 months, this has been unprecedented. I don’t think it can be easily rationalized.”

While the movements in the oil markets have been similar to swings in most asset classes, including stocks and other commodities, the recent rise in oil prices is reprising the debate from last year over the role of investors — or speculators — in the commodity markets.

Government officials around the world have become concerned about a possible replay of last year’s surge. Energy officials from the European Union and the Organization of Petroleum Exporting Countries, meeting in Vienna, Austria, in June, said that “the speculation issue had not been resolved yet and that the 2008 bubble could be repeated” without more oversight.

But unlike last year, when the economy was still not in recession and demand for commodities was strong, the world today is mired in its worst slump in more than half a century. The World Bank warned that the recession would be deeper than previously thought and said any recovery next year would be subdued.

“Crude oil prices appear to have been divorced from the underlying fundamentals of weak demand, ample supply and high inventories,” Deutsche Bank analysts said in a recent report.