Insurance Premiums, Not Mines, Are Blocking the Strait of Hormuz

The primary mechanism halting shipping through the Strait of Hormuz is a collapse in commercial insurance. The cost of covering a vessel to sail through the chokepoint has surged to about 5% of a ship's value, roughly five times pre-conflict levels. For a $100 million oil tanker, that translates to a $5 million premium, a figure that insurers say remains available but is effectively prohibitive for most owners.

This premium directly explains the traffic collapse. Since the war began, only 21 tankers have transited the route, a fraction of the more than 100 ships daily that normally pass. The high cost, coupled with safety risks, means most ship owners are unwilling to pay. Iran's Foreign Minister directly attributes the hesitation to insurer fears, blaming the U.S. for creating the conditions that make shipping too risky to insure.

The result is a de facto blockade. While Tehran appears to be selectively allowing some non-Iranian cargo through, the overwhelming majority of vessels are holding position outside the strait, creating a massive backlog. This insurance-driven halt is the core bottleneck, not a physical closure, and it underscores how financial markets can paralyze critical global trade lanes.

The Flow of Oil and the Market's Response

The physical flow of oil through the strait has collapsed to a trickle, with just 21 tankers transiting since the war began. This is a direct result of the insurance-driven halt, as most vessels remain idle in the Gulf of Oman, creating a massive backlog. The chokepoint's importance cannot be overstated: it normally carries roughly 20% of the world's oil trade, making its closure a major supply disruption.

A small number of vessels, often with Chinese or Indian ties, have been permitted to transit under negotiated safe passage. This selective routing suggests Tehran is allowing some non-Iranian cargo through, but it is insufficient to move the global market. The result is a severe supply shock, with oil producers like Iraq and Kuwait already curtailing production in early March as storage fills up and exports halt.

Market models now project a 100% probability of closure in the second quarter. The risk of a prolonged disruption, and the resulting price spike, is high. This setup creates a volatile environment where any de-escalation could trigger a swift reversal, while continued conflict would lock in a major supply deficit.

Catalysts and Risks for the Flow

The immediate catalyst for reopening the strait is a major multinational naval response. The U.S. is actively seeking allies, with Britain, France, Germany, Italy, the Netherlands, and Japan pledging to help ensure safe passage by contributing to appropriate efforts. This coordinated naval force would likely be deployed if there are direct attacks on commercial vessels or if the disruption persists, aiming to physically secure the waterway and restore confidence.

The primary risk, however, remains financial and operational. High insurance costs and safety fears will persist, keeping the strait's flow at a trickle. War-risk premiums have surged to 0.5% to 1% of a vessel's value, or even higher, which is unsustainable for most owners. Even with a naval escort, ship owners must still pay these prohibitive premiums and face significant safety risks, creating a dual barrier to transit.

This dynamic sets up a volatile equilibrium. A successful naval operation could trigger a swift reversal, with vessels rushing to cross. But if the naval effort is limited or faces resistance, the insurance-driven halt will remain the dominant constraint. The result is a market priced for prolonged disruption, where any de-escalation could spark a rapid price drop, while continued conflict would lock in a major supply deficit.