This paper differs from the existing literature as it takes into account the possibility that share repurchases are not used to serve for the general shareholders' interests. When controlling shareholders heavily use their stockholdings as a pledge for personal loans or when their cash flow rights is low, investors do not respond to the announcement of repurchases. This evidence is in favor of a personal interest hypothesis. On the contrary, the market reacts favorably to buyback programs when there are no pledged stocks or when the cash flow rights is high. The evidence is consistent with the signaling hypothesis. Evidence based on operating performances and long-run abnormal return paints the same conclusion. 本研究藉由檢測短期宣告效果，探討公司宣告股票購回是否在謀求控制股東的個人利益，而非全體股東的利益。實證結果發現，當控制股東大量使用本身持股作為個人銀行借款的擔保之用，或者擁有較少的現金流量請求權時，市場投資人會將公司股票購回的行為解讀為控制股東在謀求個人利益，因此市場不會有任何宣告效果，符合個人利益假說(personal interest hypothesis)的預期。反之，如果控制股東沒有藉由個人股票質押取得銀行借款，或者擁有較多的現金流量請求權時，公司股票購回的宣告效果則顯著為正，符合過去文獻中訊息釋放假說(signaling hypothesis)。此外，當我們檢測公司長期營運績效與長期異常報酬時，亦得到相同的結果。
