Roughly 80% of world trade by volume moves by sea, about 86.6% on the higher estimates. It is the least-visible critical system in the economy: cheap, standardized, and reliable enough that most people never think about it until a single ship wedged sideways in a canal makes the news. This note covers how the system works, where it is fragile, who controls it, and the two forces reshaping it now: deglobalization and decarbonization.
The container did it
The modern system runs on one idea: a standardized steel box that never gets unpacked between origin and destination. Before Malcolm McLean’s first container voyage in 1956, loading a ship was manual, slow, and theft-prone, and port labor was the dominant cost of moving goods. The ISO container collapsed that cost by making the box intermodal: the same unit moves ship to crane to truck to rail without anyone touching the cargo. The measure of trade became the TEU (twenty-foot equivalent unit). Global container trade reached about 183 million TEU in 2024.
Standardization also drove ships to enormous size. The economics of a container ship are close to pure scale: a vessel carrying 24,000 boxes costs far less per box than one carrying 8,000. That logic only holds in a world of safe seas and high, predictable volume. When either assumption breaks, the megaship becomes a liability, which is why Zeihan and some maritime analysts expect a shift back toward smaller ships calling at more, smaller ports. See Containerization.
Chokepoints are the fragility
A handful of narrow passages carry a wildly disproportionate share of trade, and the system has almost no slack around them. The Suez Canal alone handles around 12% of global trade and about 30% of global container traffic. When the Ever Given grounded there for six days in March 2021, each day of blockage stalled an estimated $6 to $10 billion in trade, roughly $400 million per hour, and each additional day tied up another 0.5% of global shipping capacity in queues.
The 2023–2025 stretch showed the same fragility from three directions at once. Houthi attacks in the Red Sea pushed carriers off Suez and around the Cape of Good Hope, a detour that adds roughly ten days and thousands of miles. Drought dropped water levels in the Panama Canal, forcing draft and traffic restrictions that backed up vessels. Piracy and armed-robbery incidents in the Malacca and Singapore straits jumped to 80 in the first half of 2025 from 21 a year earlier, per ReCAAP ISC, the regional reporting body. That these hit at once is a structural property, not bad luck: a network with thin buffers and long delays amplifies a local shock into a global one, and reroutings ripple back as the amplified demand swings that hit factories months later. Chokepoint risk is the live wire in near-term geopolitical risk, where Hormuz sits alongside Suez as the passage whose closure moves oil first. See Maritime Chokepoints.
The market is concentrated, and offshore by design
Container shipping is an oligopoly. After the 2M partnership between Maersk and MSC dissolved in early 2025, MSC now runs independently with about 21.6% of global capacity, Maersk and Hapag-Lloyd formed the Gemini cooperation at roughly 22%, the Ocean Alliance (CMA CGM, COSCO, Evergreen) exceeds 29% across some 1,522 ships, and the Premier Alliance (HMM, ONE, Yang Ming) holds about 12%. Those four groupings control roughly 83% of capacity, with smaller independents splitting the rest. Carriers cluster into alliances because vessel-sharing lets each carrier fill more slots on more routes without running its own full network; the flip side is pricing power and a history of service-reliability complaints.
The ownership layer is deliberately stateless. Most of the world fleet flies a flag of convenience: Panama, Liberia, and the Marshall Islands alone account for about 44% of global cargo capacity. Owners register offshore for lower taxes, lighter labor rules, and cheaper multinational crews. The practice traces to US owners registering in Panama during Prohibition to serve alcohol at sea, and it means the nationality painted on a hull often tells you nothing about who owns it or who is obligated to defend it. See Flags of Convenience.
Someone has to guard the sea lanes
One influential thesis, argued by Peter Zeihan in The End of the World Is Just the Beginning, is that open oceans are not a natural state. On this account, the US Navy has underwritten freedom of navigation globally since 1945, and that guarantee is what made high-volume, just-in-time global trade rational: ships got bigger, inventories got leaner, and supply chains stretched across the planet because the sea was assumed safe by default. Remove the guarantee, Zeihan argues, and the calculus inverts. Chokepoint states charge for passage, piracy stops being a rounding error, and shippers pay war-risk premiums that price geography back in. The claim is that the postwar order was an American security subsidy, and its gradual withdrawal, not any single crisis, is what unwinds global shipping.
Many trade economists disagree, and the base rate cuts against the strong version. Global trade has repeatedly absorbed shocks and rerouted rather than collapsed: the Ever Given cleared in six days, and the Red Sea diversions since 2023 raised costs and added weeks without breaking supply. US naval primacy has not visibly receded, and container volumes hit record TEUs in 2024. The measured pattern so far is reconfiguration, shorter and more regional supply chains, friend-shoring, redundancy, rather than an unwinding. Whether the current stress is the leading edge of Zeihan’s deglobalization or just the system doing what it has always done under pressure is the open question the thesis rests on.
Two transitions at once
While the security order frays, the industry faces a fuel problem. Shipping burns heavy fuel oil and emits close to 3% of global CO₂. The IMO’s 2023 GHG strategy set a target of net-zero emissions by or around 2050, with interim checkpoints in the 2030s and a follow-on Net-Zero Framework agreed in 2025. The candidate fuels are green methanol and ammonia, and the split is telling: the International Energy Agency expects ammonia to dominate by 2050, yet owners have ordered far more methanol-capable ships because ammonia is toxic and lacks finalized IMO safety rules. The binding constraint is bunkering, not engines: only about 120 ports can store and deliver methanol, and green methanol supply is far short of demand. Estimates put the transition cost at $8 to $28 billion per year. The open question is whether a fragmenting trade order can coordinate a fuel switch that requires globally standardized infrastructure.
Try it
Watch the fleet move in real time (1–2 hours, browser + a bit of Python). Open MarineTraffic or the free AIS feed and watch traffic density at Suez, Hormuz, and the Cape of Good Hope. Then pull historical AIS or the IMF PortWatch daily transit series and plot Suez vs. Cape of Good Hope transit counts across 2023–2025. What you are looking for is the rerouting event: a sharp drop at Suez with a matching rise around the Cape when Red Sea attacks spike. If the security-subsidy thesis holds, you will see traffic physically avoiding the cheapest route the moment it stops being safe.
Trace one product’s chokepoint exposure (an afternoon, no code). Pick something on your desk, find where it or its key inputs are made, and map the sea route to you. Mark every chokepoint it crosses. Then check the Drewry World Container Index for the spot rate on that lane. You are measuring how many single points of failure sit between a factory and your hands, and what the market currently charges to run that gauntlet.
See also
- Containerization — the standardized box that made the whole system possible
- Maritime Chokepoints — the narrow passages where the fragility concentrates
- Flags of Convenience — why most ships are registered offshore
- Bullwhip Effect — how a rerouting shock amplifies into upstream production swings
- Systems Thinking — why thin buffers plus delays turn a local shock global
- Economic and Geopolitical Risk Scenarios for the Next 3 Months — chokepoint risk as a live near-term scenario
Sources
- Maritime Transport Dominates Global Trade — the ~86.6%-by-volume figure and modal breakdown.
- Systemic impacts of disruptions at maritime chokepoints — Nature Communications (2025) on how chokepoint shocks propagate through the trade network.
- Blockage of the Suez Canal, March 2021 — Port Economics on the Ever Given and the 12%/30% trade shares.
- Shipping alliances and MSC control almost 83% of market — the post-2M alliance map and capacity shares.
- Flags of Convenience Dominate Maritime Freight — the 44% concentration in Panama, Liberia, and the Marshall Islands.
- Green fuels in shipping face major challenges for 2050 net zero — the methanol-vs-ammonia split and the bunkering constraint.