2024年11月起隨著美國政權移轉，對於外國汽車的進口關稅政策浮上檯面，其中在美國具有高市佔率的日本汽車品牌受到嚴重衝擊。

本研究使用事件研究法(Event study)對2024年11月至2025年3月與關稅政策宣告相關之四個事件日進行實證研究，根據研究結果顯示，只有在事件一-川普(Donald Trump)當選美國總統後，日本汽車產業公司之股價產生顯著之影響。川普當選美國總統後，日本汽車產業公司之股價產生較負向的累積異常報酬；同時若公司對北美洲銷貨收入佔整體銷貨收入比例愈高時，對關稅政策宣告將產生較負面的累積異常報酬。此外本研究亦發現對北美銷售依賴度高之公司可以藉由較高額之美國投資設廠金額來減緩上述關稅帶來之衝擊。

Starting in November 2024, with the transfer of political power in the United States, the issue of import tariffs on foreign cars came into focus. Japanese automobile brands, which hold a large share of the U.S. market, were hit especially hard.

This study applies the event study method to analyze four key dates related to tariff policy announcements between November 2024 and March 2025. The results show that only the first event—the election of Donald Trump as U.S. President—had a significant impact on the stock prices of Japanese automakers. After Trump’s election, these companies experienced more negative cumulative abnormal returns. The higher a company’s reliance on sales in North America, the more negative the impact of tariff announcements. In addition, the study also finds that companies highly dependent on the North American market can reduce the negative effects of tariffs by heavy investments in U.S. manufacturing plants.

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