近幾年來，許多公司理財的研究開始探討經理人過度自信對於公司財務決策的影響，例 如：投資決策、融資決策、資本結構，與購併等。研究結果顯示，過度自信的經理人容易發 生過度投資的問題、喜歡內部融資更甚於外部融資。但有關於經理人過度自信與公司股票購 回行為之間的文獻卻相對較少，本計劃將嘗試從經理人過度自信的角度切入，重新檢驗公司 股票購回文獻中提及的假說。 根據股票購回的文獻，公司的經理人會利用宣佈股票購回的機會，向外部投資人釋放公 司股價可能被低估，或者公司未來盈餘展望極佳的正面訊號。因此公司宣佈股票購回後，不 論在短期或長期，股票都會有正的異常報酬，公司的營運績效也會增加。但如果公司經理人 有過度自信的傾向，上述結果還會成立嗎？這是本計劃主要想要研究的問題。 根據行為財務學的文獻指出，過度自信的經理人會認為自己公司的股票價格被低估，並 且高估公司未來的盈餘展望。因此，如果公司的經理人有過度自信的傾向，當他(她)宣告股 票購回後，我預測該公司購回的股數將會比其他公司多。同時，投資人也會將該公司股票購 回的原因解讀為經理人認知上的偏差所致，因此不論短期或長期，股票皆不會有正的異常報 酬，公司的營運績效也不會增加。 A number of recent papers have documented several implications of managerial overconfidence in various corporate decisions, e.g. investment decision, financing decision, and capital structure, and M&A. Yet, there is no research paper examining the impact of managerial overconfidence on share repurchase. This paper examines some implications of CEO overconfidence in share repurchase. We consider an overconfident CEO who is more likely to believe that their firms are undervalued by the market and overestimate the future cash flows (Heaton, 2002). We ask whether managerial overconfidence affects the buyback behavior and how the market reacts to a share repurchase announced by an overconfident CEO. To answer our research questions, we examine stock returns, operating performance, and actual buyback shares based on firms with an overconfident CEO after repurchase announcement. The measures of CEO overconfidence are proxies by the frequency of acquisition deals by a CEO and the outsiders’ perceive of the CEO in business press. Since overconfident CEO believes that their firms are undervalued by the market, we expect that overconfident CEO will acquire more shares. Due to the managerial biases, share repurchase made by overconfident CEO should not be a credibly signal. Thus we expect that, for firms with an overconfident CEO, the stock performance and operating performance are less positive following the announcement of share repurchase.