Oil price drop is second largest on record

Oil price drop: Thursday's oil price drop was the second largest one-day drop on record. Here is what triggers these drops.

On Thursday Brent oil posted it second-largest one-day fall on record in dollar terms. Europe's benchmark crude fell by as much as $12 a barrel during the normal trading session, and U.S. crude dropped $10, leading one of the sharpest commodities sell-offs in years.

Oil's fall came amid weakening U.S. macroeconomic data, including disappointing jobs numbers on Thursday, concerns over further monetary tightening in China and eurozone debt fears.

But Thursday's drop differs from a few of the other biggest one-day oil price falls of the past, which came in conjunction with more clearly momentous economic or geopolitical events.

Following is a list of a few of the biggest one-day drops in oil prices and the events that helped to trigger them:

May 5, 2011:

Oil fell in a series of sharp dives on Thursday, dropping by a modest few dollars a barrel at first, and later gaining downward momentum to crash $12 a barrel at one point in Brent's case. Crude fell for a fourth straight day.

Weak economic data from Europe and the United States fed concerns that have hit commodities prices all week. German industrial orders fell unexpectedly in March while U.S. weekly jobless claims hit eight-month highs.

But traders and analysts were at a loss to attribute all of the selling to worsening macroeconomic trends. They said U.S. crude broke below $100 for the first time since March as technical triggers set off a cascade of sell orders.

Shelley Goldberg, a strategist at Roubini Global Economics, explained how the fall in oil prices may have been exacerbated by unloading from algorithmic traders and retail ETF investors who have flooded into commodities markets recently.

These investors, she said, can add force to bearish selling streaks once they are under way. The computer models used by algorithmic traders often direct wide-scale selling once markets start falling.

"When the trend is down, they will sell further," Goldberg said of "algo" traders with commodities exposure.

Sept 29, 2008:

U.S. crude futures drop $10.52 a barrel after the U.S. House of Representatives voted down a $700 billion plan to come to the rescue of worsening financial markets by purchasing failing mortgage securities, and in the wake of a bankruptcy filing from U.S. investment bank Lehman Bros. two weeks earlier.

On September 24, 2008, U.S. crude had posted a huge $16 a barrel one-day gain, on optimism over the prospective bailout package that was seen as potentially spurring oil demand. A massive bailout would eventually be approved.

January 17, 1991: U.S. crude falls $10.56 a barrel in response to a U.S. decision to release stockpiles of crude from its massive Strategic Petroleum Reserve to compensate for supply shortfalls amid the escalating Gulf War.

By the time the SPR release was decided, the Gulf War had already pushed crude prices sharply higher as U.S. forces bombed Iraq after its soldiers invaded neighboring Kuwait and sought to annex oil fields.