Polymarket shows 22% chance of Bab el-Mandeb Strait closure by December 31

One of the most important waterways on Earth now has a one-in-five chance of being effectively closed before year’s end, according to traders on Polymarket. The decentralized prediction market currently assigns a 22% probability that the Bab el-Mandeb Strait, the narrow passage connecting the Red Sea to the Gulf of Aden, will grind to a functional halt by December 31, 2026.

For anyone who doesn’t have a shipping map memorized: roughly 12% of global trade normally passes through this strait. When it slows down, everything from oil tankers to container ships has to take the long way around Africa, adding weeks and billions in costs.

What counts as “closed”

Polymarket’s contract uses a specific, measurable definition. The strait resolves as “effectively closed” if the International Monetary Fund’s PortWatch tool shows a 7-day moving average of ship arrivals falling to 10 or fewer. That’s a high bar, and it hasn’t been hit yet.

Current ship transits have already dropped dramatically from pre-crisis levels, with daily crossings halved on some days to roughly 15 vessels. That’s 40-60% below where traffic sat before Houthi forces began targeting commercial shipping. But 15 is still above the threshold of 10, which means the strait is battered but not formally shut.

The probability assigned by traders has fluctuated between 21% and 33% in recent weeks. Total market volume across related contracts on Polymarket has landed in the range of $5 million to $14 million, a sign that this isn’t just a novelty bet. Real money is trying to price geopolitical risk in real time.

Why the odds are climbing

The probability isn’t floating around 22% on vibes alone. In September 2026, Houthi forces captured the port of Mokha, a strategic Yemeni coastal city that gives them direct line of sight over strait traffic. They also took control of Perim Island and the Hanish islands, volcanic outcroppings that sit right in the middle of the shipping lane.

The Houthis have maintained that they are not imposing a blanket closure. Their official position is that navigation remains open to all vessels except those linked to nations they consider hostile. In practice, that distinction has done little to reassure commercial shippers or their insurers.

War-risk insurance premiums for transiting the strait have spiked to between 0.7% and 2% of hull value. For a large container ship worth hundreds of millions of dollars, that translates to per-voyage insurance costs that can easily exceed a million dollars.

Qatar has publicly warned that an effective closure of the Bab el-Mandeb would constitute a catastrophe for global energy markets. The strait is a critical artery for liquefied natural gas shipments heading from the Persian Gulf to European and Asian buyers.

The prediction market as a risk gauge

Polymarket’s geopolitical contracts have increasingly become a real-time barometer for risks that traditional financial markets are slower to price. The platform, built on the Polygon blockchain, allows traders to buy and sell outcome shares that pay $1 if a specified event occurs and nothing if it doesn’t. A 22-cent share price translates directly into a 22% implied probability.

When Houthi forces seized Perim Island, the contract repriced within hours. Traditional risk assessments from shipping consultancies can take days or weeks to update.

Rerouting around Africa adds roughly 10-14 days to voyages between Asia and Europe. The contract’s resolution date of December 31, 2026 gives traders about three months of remaining exposure. The key variables to watch are further Houthi territorial gains, any international military response, and the day-by-day ship transit data from IMF PortWatch.

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