**Introduction** Persistent US tariffs pose long-term risks to the stability of global supply chains and the credibility of trade governance by locking in fragmented production structures, sustaining high levels of trade policy uncertainty, and entrenching unilateral approaches to trade management. Since early 2025, the scale and persistence of tariff measures have been large enough to alter firm behavior and investment decisions in ways that are difficult to reverse, with implications extending well beyond bilateral trade balances[1][2]. **Long-term risks for supply chains and trade governance** **1.** **Sustained tariffs reshape supply-chain structure over time** The cumulative scale of tariff and related import measures reached **US$2,732.7 billion** in global merchandise trade coverage during the mid-October 2024 to mid-May 2025 review period, the highest level recorded since systematic monitoring began in 2009[1]. The stock of tariff increases and other import restrictions in force rose to **US$4,604.1 billion**, affecting **19.4% of world imports** by end-May 2025, up from **12.5%** at end-2024[1]. When trade barriers reach this breadth, firms adjust supply chains structurally — by changing suppliers, locations, and logistics networks — to minimize tariff exposure, embedding fragmentation and higher operating costs into global production systems[1]. **2.** **Elevated tariff uncertainty discourages cross-border investment** Import measures introduced in response to developments since early 2025 accounted for **US$2,350 billion** by mid-October 2025[2]. Average US effective tariff rates increased sharply in 2025, reflecting multiple measures with effective dates in February and March 2025 that are incorporated into baseline economic projections[3] Global macroeconomic assessments for late 2025 link higher tariffs introduced in early 2025 to elevated uncertainty surrounding trade and growth prospects[4]. Such persistent uncertainty over tariff levels and coverage reduces incentives for long-horizon investment in cross-border production networks, weakening coordination across globally dispersed value chains[2][3][4]. **3.** **Higher trade costs and reduced efficiency under sustained tariffs** Tariff persistence encourages sourcing decisions driven by policy exposure rather than cost efficiency or productivity. Rising trade barriers are identified as a channel through which trade costs increase and inflationary pressures persist, even as growth prospects weaken[3]. Over time, these shifts reduce productivity gains from specialization and limit the ability of supply chains to absorb shocks efficiently, particularly in sectors dependent on complex, multi-country production[3]. **4.** **Trade governance weakens as unilateral measures persist** Many import-restrictive measures introduced since 2009 remain in force, contributing to a growing stockpile of restrictions that reduces predictability in the trading system[1]. By mid-October 2025, the stock of import-related “other trade and trade-related measures” in force among the Group of 20 (G20) economies reached **US$4,015 billion**, covering **22.0% of G20 imports** and **16.9% of world imports**, reflecting a sharp increase linked to measures implemented from early 2025 onward[2]. Persistent tariff use also interacts with local content requirements and other industrial policy tools, reinforcing policy-driven market segmentation[5]. Sustained reliance on unilateral tariffs weakens confidence in multilateral disciplines and shifts dispute resolution toward power-based bargaining, increasing governance risks for smaller economies and globally integrated firms[1][2][5]. **Conclusion** From 2025 onward, the breadth and durability of US tariff measures have increased the likelihood that supply-chain reconfiguration becomes structural rather than cyclical. The resulting fragmentation, higher costs, and prolonged uncertainty weaken the efficiency and resilience of global supply chains, while the accumulation of unilateral measures undermines the stabilizing role of multilateral trade governance over the long term[1][2][3][4].
