為探討臺灣上市、櫃公司實施股票購回計畫之宣告效果,研究期間自2000年8月至2014年12月止,先以BCG矩陣之市場佔有率及營收成長率,將公司區分為明星事業、金牛事業、落水狗事業以及問題事業,利用事件研究法驗證公司實施股票購回後,其股價短期與長期之反應。 研究結果發現在股票購回宣告前股價被低估,宣告後則具有正向反應,不同事業的宣告強度有所差別,在短期宣告績效表現,低市佔率與低成長率的落水狗事業宣告後異常報酬最高,其次金牛事業、明星事業,最低者為問題事業;在長期宣告績效表現,高市佔率與低成長率的金牛事業宣告後異常報酬最高,其次落水狗事業、明星事業,最低者為問題事業。
To explore the announcement effect of stock repurchasing by listed and over-the-counter (OTC) firms, we divide them into Star businesses, Cash Cow businesses, Dog businesses, and Question Mark businesses according to market share rate and revenue growth rate in a Boston Consulting Group (BCG) matrix. The study period was from August 2000 to December 2014. We conduct an event study to investigate the short-term and long-term responses of stock prices after firms repurchase their stocks. The results show that stock prices are underestimated before stock repurchasing is announced; however, the announcement of stock repurchasing elicits a positive response. Announcement strength varies among various businesses. Regarding short-term announced performance, Dog businesses with a low market share rate and revenue growth rate present the highest abnormal returns after a stock repurchasing announcement, followed by Cash Cow businesses, Star businesses, and then Question Mark businesses. Regarding long-term announced performance, Cash Cow businesses with a high market share rate and revenue growth rate present the highest abnormal returns after a stock repurchasing announcement, followed by Dog businesses, Star businesses, and then Question Mark businesses.