本研究的主題在於探討多角化與企業創新能力之間的關係。在過去的相關文獻中，有些認為多角化的範疇經濟效果會加強企業的創新能力；有些文獻則認為，由於多角化企業面臨較高的代理人成本問題，使得經理人傾向追求短期利潤，而使需要長期投資的研發投資經常被忽略，反而傷害了公司的創新能力。過去的實證結果在針對多角化是否有害創新能力此一主題上，也的確呈現出不一致的結果。
　　過去的相關研究中，多採取以研發成果的總數量來做為創新的量化方式，例如獲得專利權的數目或新產品宣告的數目，不過，這樣的衡量方式忽略了創新的經濟價值，因此，在本研究採取個案研究法，利用觀察公司宣告獲得專利權當天的股價表現，來做為判斷企業創新能力的指標，並利用Hefindahl index、產品線數量、Entropy等指標來做為衡量多角化程度的方式。
　　本研究結果發現，平均而言，樣本公司在宣告日當天獲得2.77%的正向異常報酬，表示投資人的確會對將對公司的創新價值評估，反映在專利權宣告日當天的股價上。除此之外，專注化的企業在宣告日當天的股價正向異常報酬為2.93%，而多角化企業的正向異常報酬只有1.87%，這數據表示，雖然投資者對專利權宣告都保持樂觀的評價，但是他們明顯認為多角化企業的專利權價值低於專注化企業。
　　即使本研究進一步採用迴歸分析來觀察多角化與創新之間的關係，依然得到一致性的結果，多角化程度與宣告日當天的正向異常報酬呈現出顯著的負向關係，表示多角化程度愈高的企業，與專注化企業相比，創新的成果的確較不受到投資者認同。本研究還進一步發現，非相關多角化對創新能力所造成的傷害，比相關多角化企業來得嚴重，這些證據都暗示，多角化所引發的代理人成本問題，確實對企業創新造成負面的影響。

　　This study examines the empirical relation between corporate diversification and innovation. Diversification may facilitate innovation due to the economies of scope. It may on the other hand hinder innovation because of higher agency costs. Previous studies have shown inconsistent results. The difficulty of measure innovation has been argued in the past. The common approach to relate innovation is counting total innovative outputs such as patent grants or new products. However, this approach may not truly reflect innovation’s economic value. Therefore, the inconsistent results may due to the flaw of this approach. The new measurement introduced in this study is abnormal stock returns of patent grants announcements. This measurement reflects both quantity and quality of innovation. It also provides a forward-looking evaluation of innovation.
　　My results support the hypothesis that shareholders value patent grants immediately on announcements dates by revaluate announcing firms’ stock prices. The mean abnormal return on event-day is 2.77% which is significantly positive, in the full sample. Specifically, the mean excess returns on event-day for focus firms and diversified firms are 2.93% and 1.87%, respectively. The results suggest that focus firms experience significantly higher excess returns than diversified firms do. Furthermore, I adopt three measurement of diversification suggested by Comment and Jarrell (1995) and control some variables including firm size, Tobin’s Q, R&D intensity, patents granted on announcements, year dummies and industry dummies in the regression analysis. The results present a significantly negative relation between diversification and abnormal returns of patent grants announcements, which add more empirical evidence to support that diversified firms may harm innovation. Finally, I also found evidence that unrelated diversification damages shareholders’ value more seriously than related diversification does. It may imply that the incentive problem occurring among more diversified or unrelated diversified firms increases the agency costs, which might decrease the value of patent grants.

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