Eight Key South China Sea Straits Highlighted by the Center for Strategic and International Studies (CSIS)

Quick Summary

• In 2024, the total trade volume transiting the eight straits of the South China Sea reached $6.4 trillion, with the Malacca Strait and the Taiwan Strait accounting for the overwhelming majority at over $2.4 trillion each.
• According to CSIS, a blockade of the Taiwan Strait would inflict a more severe economic blow to China than a disruption in the Malacca Strait, while key U.S. allies including South Korea, Japan, and the Philippines also maintain a high level of dependence on the Taiwan Strait.
• Although alternative rerouting options exist in the event of a blockade, they entail significant increases in travel days and shipping costs, highlighting the need to reassess supply chain risks using granular, country-and-chokepoint-level data.

※ As the geopolitical tug-of-war between the United States and Iran over control of the Strait of Hormuz continues without a clear resolution, it is crucial for trade professionals and investors to meticulously evaluate supply chain risks and their implications for economic security.

This CSIS brief, published in July 2026, offers the first granular analysis of trade value flowing through eight major South China Sea straits.

In 2024, nearly $6.4 trillion in goods collectively transited these eight straits, a figure that includes double-counting for cargo crossing multiple straits.

The Malacca and Taiwan Straits stand far above the rest, each moving over $2.4 trillion — roughly 21 percent of global maritime trade apiece.

The remaining six straits (Sunda, Luzon, Mindoro, Makassar, Balabac, Lombok) handle comparatively modest volumes.

The 2026 Iran war, which severely disrupted the Strait of Hormuz, has heightened global awareness of chokepoint vulnerabilities, including in the South China Sea.

China has long worried about a “Malacca Dilemma,” but this analysis reveals the “Taiwan Strait Dilemma” is actually more severe.

In 2024, 33 percent of China’s imports and 16 percent of its exports passed through the Taiwan Strait, versus 21 percent and 14 percent respectively for Malacca.

The Taiwan Strait is also critical to China’s own domestic coastal shipping (e.g., Shenzhen/Guangzhou to Shanghai/Tianjin), making a blockade there especially damaging.

The United States itself has low direct exposure, with the Malacca, Taiwan, and Luzon Straits each carrying only 3-4 percent of total U.S. trade.

By contrast, key U.S. allies — Japan, South Korea, and the Philippines — are far more exposed, collectively shipping $755 billion through the Taiwan Strait versus $474 billion through Malacca.

Japan relies on the Taiwan Strait for 28 percent of its total trade and Malacca for 18 percent; South Korea’s figures are 22 percent and 13 percent respectively.

For both Japan and South Korea, energy imports (oil, gas, minerals) make up the bulk of what flows through Malacca — 64 percent and 78 percent respectively.

Taiwan itself is almost entirely dependent on maritime energy imports, with just two ports (Kaohsiung and Taichung) handling 72 percent of the island’s total imports — making it acutely vulnerable to blockade or quarantine.

Australia and New Zealand are outliers, relying most heavily on the Mindoro, Lombok, and Makassar Straits to export iron ore, LNG, coal, and oil. Six Gulf states — Iraq, Kuwait, Oman, Qatar, Saudi Arabia, and the UAE — each rely on the Malacca Strait for over 40 percent of their exports.

Eritrea in Africa shows the highest reliance in the world, with 90 percent of its exports passing through Malacca.

In a Taiwan Strait conflict scenario, China could reroute some shipping via the Miyako Strait, but vessels would remain vulnerable to interdiction.

Rerouting around a blockaded Malacca Strait would require detours through Sunda, then Lombok/Makassar, or in the worst case, a long path around Australia — all adding significant time and cost.

A real-world precedent: after Houthi attacks in the Red Sea, some Europe-to-Arabian Sea shipping routes nearly doubled in length, from 19 to 34 days, via the Cape of Good Hope.

The report concludes that policymakers should move beyond aggregate figures and use country-specific, strait-specific data to better anticipate the economic fallout of a potential Taiwan conflict.

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