中國制裁美光事件對DRAM產業股價之影響──台廠概念股之實證

The Impact of China's Micron Sanctions on DRAM Stock Prices: An Empirical Study of Taiwanese DRAM Concept Stocks

本研究分析中國制裁美光事件對臺灣DRAM概念股的影響。通過檢驗每日平均異常報酬，發現事件日前十個交易日中有五天P值小於0.1，呈現顯著負異常報酬，而事件日後第四天亦然。此乃投資人擔心台灣DRAM廠商在此制裁事件中受到波及，這種擔憂源于台灣DRAM廠商與美光之間的技術授權、聯合研發、供應鏈合作等長期合作關係。然而，由於台灣主要DRAM廠商如南亞科技和華邦電子與美光亦存在市場競爭關係，因此制裁事件也引發了投資人對中國可能將轉單台廠的預期，此可由事件日前第六日及第三日與事件日後第二日及第五日的P值均高達0.9以上的顯著正異常報酬得到驗證。再者累積平均異常報酬的檢驗結果顯示，事件日前有八天及事件日當天的P值均達顯著水準，反映出投資人持續關注中國在美中科技戰中的反制措施。然而，事件日後僅第四天呈現顯著，顯示由於DRAM不是台灣半導體主力的先進製程代工，在中國宣佈制裁美光後，投資人對DRAM概念股的關注度即迅速降低。

This study analyzes the impact of the Micron sanction event by China on Taiwan's DRAM concept stocks. By examining the daily average abnormal returns, it was found that there were significantly negative abnormal returns on five days out of the ten trading days before the event, with p-values less than 0.1, as well as on the fourth day after the event. This indicates that investors were concerned about the potential impact on Taiwanese DRAM manufacturers due to their long-term cooperation with Micron in technology licensing, joint development, and supply chain collaboration. However, since major Taiwanese DRAM manufacturers such as Nanya Technology and Winbond Electronics also compete with Micron in the market, the sanction event triggered investor expectations that China might shift its orders to Taiwanese firms. This expectation is verified by the significantly positive abnormal returns on the sixth and third days before the event and the second and fifth days after the event, with p-values exceeding 0.9. Furthermore, the results of the cumulative average abnormal returns test show significant p-values on the eight days before the event and on the event day itself, reflecting investors' continuous attention to China's countermeasures in the US-China tech war. However, only the fourth day after the event showed significance, indicating that, since DRAM is not the focus of Taiwan's advanced semiconductor manufacturing, investor attention to DRAM concept stocks quickly diminished after China announced sanctions on Micron.