本研究採用事件研究法，檢視自民國93年至98年，國內上市公司宣告庫藏股購回對公司股價之變動情形，並依宣告目的之不同-宣告目的1(轉讓股份予員工)、宣告目的2(股權轉換)之外及宣告目的3(維護公司信用及股東權益)，來研究其買回之長短期績效表現。實證結果發現，公司在宣告庫藏股買回前股價會出現異常下跌的現象，支持股票買回後確實存在著正向短期宣告效果。長期而言，國內庫藏股買回的公司長期的超額報酬相較於大盤指數的報酬亦顯著為正，故支持著庫藏股宣告長期效果之存在，且不論短期效果亦或是長期效果，皆以宣告目的3(維護公司信用及股東權益)的股價超額報酬率效應最為顯著，所以對投資人而言選擇投資標的時可以考慮以宣告買回目的3(維護公司信用及股東權益)之股票作為選股標的。This study adopts the standard event-study method to examine the stock price reaction to the stock repurchases of firms listed on TSEC in Taiwan from 2004 to 2009. According to different announcements- Announcement Intention 1, “granting stocks to employees.”、 Announcement Intention 2, “ownership transference,” and Announcement Intention 3, “maintenance of company credit and protection of shareholders’ interests”, we investigate - short- and long-term performance difference between stocks marked by different intentions of stock buy-back announcement. The empirical results show that: before announcements, stock prices were likely to go down abnormally, but after the announcements, the prices tended to stabilize considerably. This shows a short-term positive effect of announcements on stock prices.As for the long-term effect, it is shown that the stock prices following buy-backs outperformed the market index in the long-term. This shows a long-term positive effect of announcements on stock prices. Regardless of short-term effect or long-term effects,the abnormal returns were most salient with Announcement Intention 3(maintenance of company credit and protection of shareholders’ interests).So investors can choose the announcement Intention 3(maintenance of company credit and protection of shareholders’ interests) as an investment.
