The move has been seen widely as part of a strategy for OPEC to maintain market share and put pressure on its U.S. rival shale oil producers.
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The strategy appears to be working, with the IEA noting that the U.S oil rig count has now fallen for 26 consecutive weeks through the week ending 5 June and that quarterly reports posted by major U.S. shale drillers show how the drop in oil prices hit earnings in the first quarter of 2015.
The IEA remarked that "however remarkable the drop in the rig count may seem in its rapidity and scale, totaling nearly 60 percent since its October peak, recent improvements in drilling efficiency and productivity in key output areas are no less noteworthy."
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The U.S. is not alone in seeing supplies falling – particularly as demand is slow to pick up. But while global oil supplies fell by 155,000 barrels a day in May to 96 million barrels a day on lower non-OPEC output, the IEA said, supplies remained "at a steep" three million barrels a day above the same period last year. The IEA also forecast non-OPEC supply growth to increase by 1 million barrels a day in 2015.
It also revised up its estimate of global demand growth to 1.7 mb/d for the first quarter of 2015 and 1.4 mb/d for 2015 as a whole. Sounding a note of caution, it added that "momentum is expected to ease somewhat in the second half of 2015, assuming a return to normal weather conditions and given a recent partial recovery in oil prices."