蔓延效果或競爭效果？以事件研究法探討專利侵權訴訟宣告之衝擊

Contagion or Competitive Effect? An Event-Study Approach to Uncover the Impacts of Patent Infringement Litigation Announcement

近十年來專利訴訟案件有爆發性的成長，然而探討專利侵權訴訟和市場反應的理論缺口仍然存在。本研究之目的在於瞭解專利侵權訴訟宣告是否對被告廠商和其競爭廠商之股價和交易量產生影響。以1997-2008年78個與台灣廠商相關的專利訴訟案件為調查對象，本研究發現專利侵權訴訟宣告將對被告廠商之股價和交易量帶來負面影響。除此之外，本研究也觀察到被告廠商之競爭廠商的股價和交易量亦呈現與其相似的走勢，此一現象顯示來自專利侵權訴訟資訊之信號發射效果（蔓延效果）遠大於競爭效果。

While an explosive growth of patent litigation events in the last decade, there is still a theoretical window on exploring the relationship between patent infringement litigation announcement and the market responses. This study aims at investigating whether a patent infringement announcement would have influences on the stock price and trading volume of the defendant firm and its rival firms. Using 78 patent litigation events related to Taiwan electronics industries from 1997 to 2008, we find that patent litigation infringement announcement would bring negative impacts on both the abnormal returns and the trading volume of the defendant firm’s stock. Moreover, this study observed that there are similar market responses on the competitive rivals of the defendant firm, indicating that the information-signaling effect resulting from patent infringement litigation outweighs the competitive effect.