Brent Crude traded above $87 a barrel on Friday 17 July, a one-month high and a rise of more than 14 per cent on the week 1. Transits through the Strait of Hormuz fell to eight vessels on 16 July, down from 15 the day before and against a pre-war baseline above 100 2. Roughly a fifth of the world's seaborne oil normally passes through that channel.
War-risk premiums, the surcharge underwriters levy for sailing dangerous waters, now run at 3 to 10 per cent of hull value against 0.25 per cent before the war 3. An owner who paid $250,000 to insure a $100m hull through the strait is now quoted between $3m and $10m for the same passage, which exceeds what most single cargoes earn. No physical barrier has been placed across the water. the strait shuts on an underwriter's spreadsheet before it shuts on anything else, and the IRGC's mining claim of 18 July, which CENTCOM called false , moves that spreadsheet whether or not a single mine is ever recovered.
That asymmetry favours Tehran. Laying enough ordnance to physically close Hormuz is beyond what Iran can sustain under nightly bombardment; making insurers behave as though it might is not. Tehran can assert a minefield for the price of a broadcast, and the premium moves on the assertion.
