Hormuz Shock: Trapped Volume and the New Trade Cost Structure

The physical disruption is stark. As of 12 March, more than 85 large oil tankers are trapped in the Persian Gulf, carrying at least 21 billion litres of oil. This blockade stems from Iran's closure of the Strait of Hormuz following attacks by Israel and the U.S. on 28 February, a chokepoint that carries around one quarter of global seaborne oil trade.

Yet the trade is not entirely halted. Evidence shows a rerouting anomaly: Iran's crude oil trade largely had been uninterrupted this week, with suspected tankers seen loading at the Kharg Island terminal. This indicates that while the strait is shut to most traffic, some sanctioned Iranian exports are still flowing out, likely via alternative, riskier routes or by special U.S. waiver. The trapped volume represents a massive, concentrated risk.

The strategic importance of the Strait magnifies the shock. With commercial vessel traffic through the passage plummeting to just two transits on Monday from an average of 138 per day, the trapped volume represents a massive, concentrated risk. The immediate market reaction was clear, with Brent crude rising above $90 per barrel as the energy market priced in the severe supply constraint.

The Flow: Insurance, Freight, and Volatility Spikes

The energy market's immediate reaction was a clear price signal. Brent crude rose above $90 per barrel as the physical shock to supply became a financial one. This spike reflects the market pricing in a severe, concentrated constraint on the world's most critical oil chokepoint.

The shock is now translating into direct cost increases across maritime trade. Maersk has implemented an emergency freight increase to cover the higher operating costs from rerouting and security risks. At the same time, war risk insurance premiums are surging, adding a new layer of expense for any vessel navigating the region. These are not abstract costs; they are flows that will be passed down the supply chain.

The impact extends beyond oil. The Strait carries around one third of global seaborne fertilizer trade, a vital input for agriculture. Disruptions here threaten fertilizer access, particularly for poorer nations, and will likely drive up costs for that sector. The initial volatility is just the start of a broader cost structure reset for global shipping.

The Era: Contextualizing as the Fourth Shock

This is not a temporary spike. The costs of rerouting and war risk are now embedded in the flow, creating a new persistent cost structure. The market has already priced in the initial shock, with Brent crude settling above $90. The real story is the shift in the underlying trade economics, where every voyage through the region now carries a built-in premium for security and alternative routing.

Contextually, this joins a recent pattern of supply shocks. The pandemic and the Ukraine war both caused severe, long-lasting disruptions to global trade, with freight rates and insurance premiums spiking and staying elevated for years. The current situation at Hormuz shares that DNA: a geopolitical event has forced a costly, permanent reconfiguration of maritime routes, adding a new layer of expense that will flow through to consumers.

Global growth is projected to slow to 3.1% in 2026, a period of already strained supply chains. Adding a new, persistent cost structure to global shipping during a slowdown is a direct pressure on inflation and corporate margins. The key watchpoint is the tanker backlog. If the closure clears quickly, the cost structure may normalize. But if the blockade becomes sustained, the emergency freight increases and war risk premiums will become the new baseline, forcing a permanent recalibration of global trade flows.