International trade depends on a handful of mandatory passages – straits, canals, and capes – that concentrate enormous volumes of goods, oil, and raw materials.
As Ispi highlights, dedicating one of its in-depth reports to the topic, when one of these “chokepoints” is closed or even just threatened, the consequences ripple through prices, supply chains, and global growth.
Starting from the current crisis in the Strait of Hormuz, the Ispi report retraces the lessons of history, analyzes the most critical points, and explains why the IMF monitors as many as 28 bottlenecks. Because in an increasingly tense world, these straits are not just waterways: they have become geopolitical levers capable of fragmenting the global system.
The lesson of Suez
It is not the first time that a major maritime passage suddenly turns into an insurmountable bottleneck.
On June 5, 1967, at the outbreak of the Six-Day War, Egypt closed the Suez Canal and mined it to turn it into a defensive barrier. Fifteen ships of eight different nationalities remained trapped inside for eight long years, until its reopening after the Yom Kippur War in 1973.
During those months, oil tankers and cargo ships were forced to circumnavigate the entire African continent via the Cape of Good Hope, nearly doubling distances, times, and costs.
Today that cape has come back into the spotlight due to Houthi attacks in the Red Sea, which have pushed many companies to completely avoid the Red Sea and Suez.
Hormuz, the funnel without immediate alternatives
Unlike Suez, the Strait of Hormuz offers no quick escape routes. It is the only exit point for oil and gas from the Persian Gulf, which account for about one-fifth of the global hydrocarbon trade.
A total closure, or even just Iranian control imposing tolls, would create a very dangerous precedent for freedom of navigation.
Existing land infrastructures – the Saudi East-West pipeline and the Emirati one – are not capable of absorbing the necessary volumes. For this reason, solutions are being sought: Iraq has already started land routes towards Syria to ship oil in the Mediterranean, while more ambitious projects are taking shape such as a new pipeline to the Turkish terminal of Ceyhan.
The idea of extending pipelines all the way to Israel remains politically very complicated, despite recent rapprochements between Tel Aviv and some Gulf countries.
The 28 bottlenecks monitored by the IMF
The IMF, through its PortWatch system, keeps under observation 28 major maritime bottlenecks.
These are natural straits, artificial canals, and capes that, if blocked by conflicts, accidents, or political tensions, risk paralyzing entire production chains. Among these are not only Suez and Hormuz, but also Panama, Gibraltar, Bab el-Mandeb, the Bosporus, and numerous passages in East Asia.
These points concentrate impressive percentages of global traffic. Their vulnerability derives from physical geography, but above all from the concentration of energy flows and containers.
A closure does not only affect neighboring countries: it generates domino effects on freight rates, insurance premiums, energy prices, and inflation worldwide.
Malacca, Asia’s superhighway
Among the most delicate points is the Strait of Malacca, a 900-kilometer funnel between Malaysia, Singapore, and Indonesia that connects the Indian Ocean to the South China Sea.
Over a quarter of global trade by volume passes through here, with an average of about 440 ships per day including oil tankers and container ships. It is the main energy supply route for China and much of East Asia.
Unlike Hormuz, Malacca has alternatives in the Indonesian archipelago: the Sunda Strait, though too shallow for many large ships, and the Lombok Strait, deeper but significantly lengthening the route.
Even a simple partial restriction would cause transport costs to explode and disrupt the scheduling of Asian refineries. Not by chance, a few weeks ago the idea of introducing a shared toll among Indonesia, Malaysia, and Singapore was even floated – then denied.
The Chinese Sea: the hottest point on the map
The densest and most dangerous theater remains the Chinese Sea. Here several critical bottlenecks concentrate: the Bohai Strait, through which almost 18% of global trade passes, Taiwan Strait (16.9%), and Luzon Strait (11.8%).
In these waters daily logistics, geopolitical rivalries, and China’s strategic ambitions intertwine.
Ongoing tensions with the Philippines, the centrality of Taiwan, and the growing militarization of the region make these passages extremely sensitive. And a physical closure is not even necessary: a credible threat alone is enough to cause insurance premiums and maritime freight rates to soar, with immediate repercussions on global energy costs.
From infrastructures to instruments of power
The Hormuz crisis risks opening a Pandora’s box. If a country like Iran decided to control a mandatory passage and impose conditions or tolls, other states overlooking strategic chokepoints could follow suit, eroding the principle of freedom of navigation enshrined in international treaties.
In an increasingly fragmented world, the 28 bottlenecks are no longer just waterways connecting markets: they have become potential levers of geopolitical pressure.
The resilience of global trade will depend on the ability to diversify routes, invest in alternative land, rail, and maritime infrastructures, and strengthen cooperation to protect these vital passages.
