Houthi advance on Bab al-Mandab exposes Eritrea most by share and China most by dollars

Eritrea's share and China's dollar figure measure different things ^{[8] [11]}. The first is the fraction of a country's maritime trade, by value, that passes through the strait. The second is a sum, and the large economies dominate it. After China come India at US$243 billion, the United States at US$226 billion, Germany at US$208 billion and the United Kingdom at US$190 billion ^[11]. In dollars, China's exposure is about 2.3 times America's ^[1]. The researchers give shares for the small, nearby states and dollar sums for the big trading economies, so any single list of who is hit hardest mixes two scales ^[7].

The denominator is built broadly. The authors count as a country's maritime trade both cargo loaded at its own ports and goods carried in from foreign ports and along connected sea routes ^[10]. This is why landlocked South Sudan, at 65%, and Chad, at 61%, rank among the five most reliant states ^[8]. Yemen, on the strait's eastern shore, relies on the Red Sea for 54% of its trade by value ^{[3] [9]}. For a question about a shipping lane this is a sensible design, because a landlocked importer's goods still cross the strait before they reach a neighbour's port. The thing it doesn't tell you is how much of that trade could switch to another route, and at what price.

Losses are estimated in aggregate. By the researchers' calculation, a 30-day blockade works out to about US$1 billion a day ^{[12] [2]}. Stretching it to 45 days lifts the total to US$40 billion, so the extra 15 days add roughly US$0.67 billion a day ^{[12] [2]}. Fuel burned on longer routes, higher freight rates and rising insurance premiums make up the bill ^[12]. According to the source, the scenario is a Houthi blockade of Bab al-Mandab, and it does not say whether the model assumed Hormuz was also shut, as it has been since February ^[5].

Shipping counts show how much diversion came before the current fighting. PortWatch's September 20 figure is about 31% of the pre-2023 daily average and about 27% below the average just before the recent escalation ^{[17] [3] [6]}. Of the 48 daily transits lost since 2023, about 40, or 83%, had gone before that escalation ^[4]. A single day set against averages is a thin basis for a trend.

Many operators switched to the route around Africa after the attacks that began in late 2023, which the Houthis said were in support of Gaza ^{[13] [14]}. Some returned to the Red Sea in the years since, and others never did ^[14].