本文針對有聘任獨立董事，且在獨立董事聘任前後均有至大陸投資的台灣上市公司，探討其在獨立董事聘任前後的投資宣告效果是否有所差異，結果發現獨立董事聘任之後的宣告效果顯著優於獨立董事聘任之前的宣告效果，此一結果支持獨立董事的監督機制，有助於降低公司因代理問題所引發過度投資的疑慮。此外，我們進一步針對代理問題較為嚴重或監督機制較為薄弱的公司，探討其大陸投資的宣告效果是否會因獨立董事的聘任而有所差異，結果亦顯示，這些公司的大陸投資宣告效果，在獨立董事聘任之後有顯著的提升。本文所稱的潛在代理問題較為嚴重或監督機制較為薄弱的公司，包括成長機會較低、資訊不對稱程度較大、董事會持股比率較低、法人持股比率較低以及董事長身兼總經理的公司和家族企業。

Using a sample of Taiwan listed companies, we examined whether a company’s announcing of an intention to invest in mainland China would have a better effect on stock prices if independent directors are already appointed. Our results showed the announcement had a significantly better effect on stock price when independent directors were already appointed, suggesting that having independent directors in place can strengthen the ability of the board to supervise corporate investment decisions and reduce shareholder anxiety about the possibility of overinvestment. In addition, focusing on companies that already have independent directors in place, we also investigated the effect of such an announcement in those companies with more serious agency problems or weaker supervision as is found in firms which have less growth opportunity, which have a
larger degree of information asymmetry, which have fewer shares owned by
members of the board of directors or institutional investors, or whose chairman of the board also serves as their CEO or in firms that are family controlled. We found that such companies can expect an announcement of intention to invest in mainland China to have a better effect on stock prices if they have already appointed independent directors.