探討公司多角化與資訊不對稱問題：以庫藏股宣告事件為例

Abstract

由於早期文獻將多角化造成財務報表上相對較不透明，視為造成多角化折價的原因之一。但近期亦有學者持相反意見，認為多角化反而能夠減輕資訊不對稱的問題。故本篇論文主要欲探討公司多角化對資訊不對稱問題的影響。利用美國從1996年到2005年之間宣告公開購回庫藏股的707家公司為樣本，其中287家為多角化公司、420家為單一部門公司，檢驗transparency hypothesis, information hypothesis和inefficient investment hypothesis三個假說。以事件研究法檢定樣本，並透過橫斷面回歸方法進行分析，實證結果發現異常報酬率與衡量多角化之變數呈負向關係，即多角化公司的異常報酬率顯著高於單一部門公司。因此本研究的結果傾向支持transparency hypothesis: 多角化公司資訊不對稱的情況較單一部門公司來得嚴重。另一方面，本文亦加入衡量公司多餘資金的變數為控制變數，以分析多角化公司是否有投資不效率之情形，進而影響到庫藏股宣告的異常報酬率。結果發現，各變數的係數符號並不一致，故本文無法支持inefficient investment hypothesis。

Empirical studies of how corporate diversification affects the information asymmetry problems have been scanty. The contribution of this paper is to examine the relation between diversification and asymmetric information problems by testing announcement returns of share repurchase programs. In this paper, we utilize Thomas (2002) two hypotheses to explain the predicted results. One is the transparency hypothesis and the other is the information diversification hypothesis. In addition, we supplement with the inefficient investment hypothesis. In the cross-sectional regression, the coefficient on asset-based Herfindahl index is significantly negative. The result supports the transparency hypothesis. That is, the conglomerate form of organization makes the accounting figures more complex and less transparent. Therefore, diversification makes the information asymmetry problems more severe. As for the inefficient investment hypothesis, the coefficients on different overinvestment proxies are mixed. Thus, the effect of overinvestment problem is inconclusive.