從直接依賴到間接依賴、美中貿易戰下的GVC繞道與供應鏈重組

Abstract

本研究探討美中貿易戰是否真正降低了美國對中國生產體系的依賴，抑或僅改變了貿易的地理路徑。自 2018 年美國對中國商品加徵關稅以來，美國自中國的直接進口顯著下降，然而美中貿易逆差仍維持高位，且美國整體貿易逆差持續擴大，顯示貿易戰可能主要改變了表層貿易流向，而未完全削弱底層生產依賴關係。 本文以2003–2024年17個主要第三國之追蹤資料（374筆觀察值）為研究對象，分別從再出口與全球價值鏈（Global Value Chain, GVC）兩個層面分析美中貿易戰對供應鏈重組之影響。再出口部分以香港為代表，觀察其轉口功能之變化；全球價值鏈部分則結合HS6貿易資料與BEC分類，採用泊松擬最大概似估計法（Poisson Pseudo Maximum Likelihood, PPML）與固定效果模型，首先建立中國對第三國中間品、資本品與消費品出口與美國自第三國進口之基準關聯，並透過分時期分析、異質性分析、滯後模型、替代市場檢驗及長差分模型，探討貿易戰後供應鏈重組之特徵與可能機制。本研究聚焦於貿易戰前後關聯趨勢之變化，而非識別嚴格因果效果。 研究結果顯示，香港作為傳統轉口樞紐的重要性於貿易戰後明顯下降，反映傳統再出口模式逐漸弱化。然而，全球價值鏈分析發現，中國對第三國中間品出口與美國自第三國進口之間存在穩健的正向關聯，且分時期結果顯示，貿易戰後該關聯較戰前更為明顯，顯示中間品貿易可能已成為供應鏈重組的重要途徑。異質性分析進一步指出，此現象主要集中於人均所得較低及與美國簽署自由貿易協定（FTA）之國家，顯示第三國承接效果具有明顯差異；滯後模型與多項穩健性檢驗亦支持本文主要發現。 本研究指出，美中貿易戰主要改變了貿易的地理路徑，而非根本性的生產依賴關係。中國產能仍可能透過 GVC 分工與中間品貿易持續嵌入中美供應體系，美國在降低對中國直接依賴的同時，並未完全切斷透過第三國轉接之間接連結。

This study examines whether the U.S.–China trade war has genuinely reduced the United States' dependence on China's production system or has instead primarily altered the geographical routing of trade. Since the United States imposed additional tariffs on Chinese goods in 2018, direct U.S. imports from China have declined substantially. Nevertheless, the bilateral trade deficit has remained large, while the overall U.S. trade deficit has continued to expand. These developments suggest that the trade war may have primarily changed the observable patterns of trade flows without fully weakening the underlying production dependence between the two economies. Using a balanced panel of 17 major third-country economies covering the period 2003–2024 (374 observations), this study investigates supply chain restructuring from the perspectives of re-export trade and global value chains (GVCs). The re-export analysis focuses on Hong Kong and examines changes in its role as a traditional entrepôt. The GVC analysis combines HS six-digit trade data with the Broad Economic Categories (BEC) classification and employs the Poisson Pseudo Maximum Likelihood (PPML) estimator with fixed effects. The analysis first establishes the baseline relationship between China's exports of intermediate, capital, and consumption goods to third countries and U.S. imports from those economies. It then examines the characteristics and possible mechanisms of post-trade-war supply chain restructuring through period-specific analysis, heterogeneity analysis, lagged specifications, alternative-market tests, and long-difference models. The study focuses on changes in the relationship before and after the trade war rather than identifying strict causal effects. The results indicate that Hong Kong's importance as a traditional re-export hub declined markedly following the trade war, reflecting a gradual weakening of the conventional re-export model. The GVC analysis further reveals a robust positive relationship between China's exports of intermediate goods to third countries and U.S. imports from those economies. Period-specific estimates show that this relationship is more pronounced in the post-trade-war period than in the pre-trade-war period, suggesting that intermediate-goods trade may have become an important channel through which supply chains have been restructured. Heterogeneity analysis further indicates that this positive relationship is primarily observed among lower-income economies and countries that have free trade agreements (FTAs) with the United States, suggesting substantial differences in third countries' capacity to absorb supply chain relocation. The lagged model and a series of robustness checks provide additional support for the main findings. Overall, the findings suggest that the U.S.–China trade war has primarily reshaped the geographical routing of trade rather than fundamentally reducing production dependence. China may continue to remain embedded in the U.S.-oriented supply chain through GVC specialization and intermediate-goods trade. Consequently, although the United States has reduced its direct dependence on imports from China, indirect production linkages operating through third countries have not been fully severed.