本研究主要探討公司多角化策略類別對權益價值之影響。本研究使用Worldscope和Datastream兩種資料庫，資料樣本為從2001年到2010年全球來自47個國家的20,454間公司。本研究參考Berger and Ofek(1995)之超額價值方法，改以市價淨值比與本益比重新計算超額權益價值，做為權益價值之代理變數，並使用回歸分析去比較多角化公司與非多角化公司的權益價值，發現多角化策略能增加權益價值
本研究進一步使用Jacquemin and Berry (1979) 提出的Entropy指數將公司多角化拆解成相關多角化與非相關多角化，並使用回歸分析去檢驗不同多角化策略與權益價值的個別關係。本研究發現，相關性多角化和非相關性多角化皆與權益價值呈U字型的曲線關係，也就是在某程度下的多角化對權益價值的影響是負向的，然而當多角化達到某個程度後，其對權益價值的影響是正向的。

This study examines the impacts of different diversification strategyupon the equity value.This study uses international data from 2001 to 2010. We use Worldscope and Datastream databases, and there are 94,951 firm-years from 47 countries. We modify the excess firm value model proposed by Berger and Ofek(1995) and use price-to-equity and market-to-book ratios to calculate excess equity value. This study uses robustness check to examine whether corporate diversification has positive effect on equity value. And the result shows that equity values of diversified firms are larger than their undiversified counterparts.
Moreover, we use Entropy index addressed by Jacquemin and Berry (1979) to divide corporate diversification into related and unrelated diversification. And we use robustness checks and regression models to examine the relationship between each type of diversification and equity value. This study finds that the relationships between related diversification and equity value and between unrelated diversification and equity value are U-shaped curves. It means that equity value decreases up to a certain level of related and unrelated diversification, but beyond that level it increases as related or unrelated diversification increase.

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