OPEC+ Share of Global Oil Output Falls to 40% as Hormuz Closure Strips Cartel's Market Grip
Six months of Iran war have cut OPEC+ output by a quarter, leaving China's purchase decisions as the main variable traders are pricing.
Six months after the U.S. and Israel attacked Iran in late February, OPEC+ accounted for roughly 40% of global oil output in July, down from more than 48% before the conflict began, according to Reuters calculations based on IEA data. ICE Brent crude front-month was trading at $88.68 per barrel on Thursday (2026-08-27), holding below the $90 level it briefly breached in July as Hormuz tensions spiked, per the Kobeissi Letter.8,6
About four to five percentage points of the OPEC+ share decline came from the UAE's withdrawal from OPEC in May. The remainder reflects the direct cost of the Strait of Hormuz closure, which previously carried nearly 20% of global oil supply and roughly a quarter of worldwide seaborne oil trade. OPEC+ itself reported daily production fell to 33 million barrels per day, against nearly 43 million before the conflict.8,5,4
That production collapse puts the cartel in a position not seen since the mid-1980s, when North Sea, Alaskan and Siberian output diluted its grip after a peak of roughly 50% during the 1970s oil crises. Then, the mechanism was new supply from outside the bloc. Now it is a physical chokepoint members cannot route around by voting on quotas.8
Seven OPEC+ nations, including Saudi Arabia and Russia, agreed on Sunday (2026-05-03) to increase output by 188,000 barrels per day starting in June. Rystad Energy analyst Jorge Leon said he expected the group to pursue a similar increment at subsequent meetings. The vote had the trappings of market management. Analysts were less convinced.3,4
"Any announced production increases or changes to output targets will have limited practical value," said Ole Hansen, commodities analyst at Saxo Bank. With the Hormuz passage closed, barrels that members pump cannot reach buyers by the most direct route, rendering quota decisions largely academic for as long as the military situation persists.4
OPEC lowered its demand growth forecast for 2026 to around 1.2 million barrels per day in its Wednesday (2026-05-13) monthly update, down from about 1.6 million barrels per day previously, citing the conflict's drag on global economic activity. The cartel also reported its own production fell more than 30% since the war's start.2
Into that vacuum, China's role has shifted sharply. During the same period last year, Chinese buying may have accounted for as much as half of global oil demand growth, providing a reliable floor under prices, according to June Goh, cited in Reuters reporting. Since the war began, China has purchased roughly 400 million fewer barrels than in the comparable prior-year period. "They've become the swing demand centre," Goh said.8
When Chinese buying was surging, it offered OPEC+ a demand backstop that cushioned supply decisions. With Chinese purchases sharply reduced, the alliance loses that buffer at exactly the moment its own output is constrained. Brent has stayed elevated — the front-month contract at $88.68 per barrel on Thursday (2026-08-27) — not because OPEC+ is managing supply effectively, but because physical disruption is doing it involuntarily.8,6
China and Russia have grown more visible diplomatically since the conflict escalated. Russia lost its main Middle Eastern foothold when the Assad government fell in Syria in December 2024, and the Iran war has opened new potential avenues for both powers in the region, according to OilPrice.com reporting. Whether those moves translate into durable energy trade rerouting is not yet clear from available data.7
SEB's chief commodities analyst Bjarne Schieldrop described the situation bluntly: "It has become quite clear now that this is the biggest bluff in history and it has gone horribly wrong." The comment referred to the original escalation calculus, but it applies with some force to OPEC+ quota decisions too. Voting to raise output when the export route is closed does not restore market influence.1
The bearish case rests on demand and any easing of the physical constraint. If the Hormuz disruption resolves, volumes that have been bottled up could move quickly into the market, and Chinese demand has not rebounded to provide offsetting support. ICE Brent front-month has not broken decisively above $90 since the July spike, suggesting the market is pricing some probability of resolution.6,8
Whether Chinese buying resumes at anything close to last year's pace now sits at the centre of the supply-demand arithmetic. If it does not, OPEC+ regaining its pre-war market share percentage may prove insufficient to keep prices firm, particularly if any Hormuz easing simultaneously unlocks deferred supply.8