公司型態下，企業的經營權與所有權分離，代理問題從中而生，當經理人與股東的利益不一致時，經理人不會重視公司的資本結構是否穩健，也不在乎投資案是否可以增加公司價值，只追求自己利益的最大化。以往的研究只探討公司價值與資本結構的關係，或是只探討代理問題與公司價值的關連性，實際上，這三者之間是相互牽動的，當經理人調整公司資本結構時，不但可以看出公司價值的變化，更可以降低代理成本，因此未能同時考慮到資本結構、代理問題與公司價值的相互連動關係，所得的結論容易有偏誤。本研究以1991∼2003年間台灣上市公司為研究對象，但排除銀行、證券、產險、壽險等公司，探討公司價值、資本結構與代理問題三者之間的關連性，主要採用聯立方程式之三階段最小平方估計法（Three-Stage Least Squares, 3SLS）來研究三者相互影響之效果。

實證結果發現負債比例越高的公司，公司價值會因此降低，而代理成本越高的公司，公司價值也較低，但是代理問題可以藉由適當的舉債，以降低對公司價值的負向影響。而公司價值越高，代表資產利用率相對較高，但是，需預防公司獲利之後，經理人開始增加特權消費，裝潢豪華的辦公室、購買豪華轎車、增加薪資等，代理成本隨之而生，值得加以重視。若從產業來看，電子業公司的負債比例影響公司價值的程度較大，即負債比例過高，會降低公司的價值，但非電子業的公司，適當的增加負債比例可以降低代理問題對於公司價值的影響。此外，有形資產比率低時，更能透過舉債降低代理問題對於公司價值的影響，因台灣許多公司所面臨的，是投資不足的問題，而適當的舉債，讓公司可以作最佳的投資，反而會提升公司的價值。

Corporations are subject to agency problems resulting from the separation of ownership and control. When the managers and shareholders’ interests are not consistent, managers will not care whether capital structure is stable, and furthermore will not mind if the project would improve firm value or not. The only thing managers concern about is to maximize their own benefit. Previous work only discusses the relation between firm value and capital structure, or the connection between agency problems and firm value. However, capital structure, agency problems and firm value are multi-connected. When managers adjust firm’s capital structure, firm value changes and agency costs decreases. This research examines the relation among firm value, capital structure, and agency problems of Taiwan listed companies from 1991 to 2003, excluding banks, securities, and insurance company. We address the potentially endogenous relation among these variables by estimating a three-stage least squares regression model.

The empirical results show that the higher the debt ratio, the lower the firm value, and the higher the agency costs, the lower the firm value. Nevertheless, raising debt can mitigate the effect of agency problems on firm value. The higher firm value implies the better asset utilization. However, after firms’ gaining profit, managers might abuse discretionary expenses, such as luxurious office, cars, and upper salaries leading to serious agency costs. In the industry aspect, debt ratio of electronic industry hurts firm value. But in the non-electronic industry, debt can mitigate the effect of agency problems, especially for firms with low tangible asset ratio, because many companies in Taiwan are facing underinvestment. Raising debt will force firms to select the best portfolio and then increase the firm value.

第一章 緒論 1
第一節 研究動機 1
第二節 研究目的 2
第三節 研究架構 3
第二章 文獻探討 4
第一節 公司價值的相關研究 4
第二節 資本結構的相關研究 9
第三節 代理成本的相關研究 15
第三章 研究方法 20
第一節 研究樣本 20
第二節 變數定義 21
第三節 實證模式 24
第四章 實證分析 26
第一節 敘述統計量分析 26
第二節 相關分析 28
第三節 一般迴歸分析 34
第四節 三階段最小平方法 40
第五節 分組比較 50
第五章 結論與建議 60
參考文獻 62
中文部分 62
英文部分 63

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