先前的研究多著重在公司多角化是否會影響公司價值，Lang and Stulz (1994) 提出多角化可能會減損公司價值，而Villalonga (2004b) 則從不同的衡量方法中多角化不會造成折價的現象。因此，Santalo and Becerra (2008) 針對產業特性的部分，提出當公司多角化進入的產業具有較少的競爭者專精在該產業的話，多角化不但不會造成折價反而會有溢酬產生。因此我以投資者的角度延伸探討Santalo and Becerra (2008) 的論點，並作更進一步的測試當公司多角化進入專精競爭者較少的產業，是否會有較好的股價表現。實證結果發現，當公司多角化進入新產業，該產業中專精競爭者的數量與多角化公司的異常報酬呈現顯著且負向相關的關係，此結果也支持Santalo and Becerra (2008) 提出的論點。

Previous studies focus on the whether M&As influence the corporate value or not. Lang and Stulz (1994) point out that diversification may destroys the firm value. However, Villalonga (2004b) finds evidence of a diversification premium by using different measurement. Santalo and Becerra (2008) find that firms enjoy a premium in those industries in which only a few focus firms compete. To measure whether the argument that firms diversifying into industries with more diversified rivals are expected to experience greater stock market reactions than those into industries with more focused rivals is considered by investors or not. I follow the Santalo and Becerra (2008) idea to interpret and discuss the results. Moreover I highlight the theoretical and practical implications in my findings. The result shows that firms diversifying into new industry, the number of focus firms are significantly and negatively correlated with abnormal return of acquiring firm. The evidence is robust to different event windows and different measure of control variables. The result supports the idea of Santalo and Becerra (2008).

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