LONDON: In 2013 and early 2014, the growing imbalance between supply and demand in the oil market was masked by a string of supply disruptions as a result of war, unrest and sanctions.

After a decade of high oil prices, supplies from North American shale plays were growing by more than 1 million barrels per day annually, while fuel demand in the US and other advanced economies was more than 8 million barrels per day below its pre-2005 trend.

Only strong growth in demand from emerging markets and an increasing number of supply interruptions in the Middle East and North Africa kept the market balanced and benchmark prices over $100 per barrel.

When insurgents failed to stop Iraqi oil exports in June 2014, and Libyan exports resumed from Tobruk, the full extent of the imbalance was laid bare and prices started their vertiginous fall.

Ultimately, prices must remain low enough for long enough to slow the growth of shale output and spur increased demand for gasoline and diesel from motorists, truckers and airlines.

The adjustment is now well underway, with the number of rigs drilling for oil in the US down by almost 25 percent since October.

The causes of the price plunge, and what happens now, are discussed in a new paper written by journalists from across Reuters and released on Friday.

— John Kemp is a Reuters market analyst. The views expressed are his own.