Forty ships crossed Bab al Mandeb on the day Brent went through $100

Forty. That is how many commercial vessels transited the Bab al Mandeb Strait in the 24 hours to the afternoon of July 23, according to ship tracking data cited in the daily Iran Update published by the Institute for the Study of War and the Critical Threats Project at the American Enterprise Institute. It is more than the day before, not fewer.

The series is short and it moves in one direction and then back. Between 2:00 PM ET on July 20 and the same hour on July 21, the assessments counted 64 transits. In the following 24 hours the count was 30. In the 24 hours after that it was 40. The Houthis declared their blockade of Saudi Arabia on July 20, which is the day the first of those windows opens, and the July 23 assessment describes the current level as a significant decrease against transits before the announcement, while stating that traffic through the strait continued.

That sits oddly beside the day's price. Brent crude settled at $100.69 a barrel on Thursday, up 7 percent and the first settlement above $100 since May 26, after the Houthis claimed attacks on two Saudi tankers in the Red Sea.

The attacks themselves are now confirmed by a third party. United Kingdom Maritime Trade Operations said on July 23 that an unspecified Saudi-flagged tanker had been attacked with what it described as an unknown projectile, according to the assessment, and Saudi state media had reported on July 22 that a Houthi attack caused a fire aboard the Encelia with no casualties. Houthi officials have said they will maintain the blockade until Saudi Arabia lifts its own blockade of Yemeni ports and airports.

One earlier vessel movement is worth holding on to, because it is the pattern in miniature. The assessments recorded the tanker Xin Long Yang, carrying crude from the Saudi export terminal at Yanbu, changing course on July 21 to avoid the strait, then turning back toward it on July 22.