本文旨在探討投資者是否會依據宣告買回時內部人淨交易之情況及宣告買回股票目的的不同，而在宣告後的短期及長期有顯著的不同異常報酬。本篇研究先把內部人交易分為淨買入與淨賣出兩組，並把觀察時間拉長至宣告後第三年，分別分析這兩組在長短期的股價異常報酬。之後，再把以上模組依照買回股票目的去分群，以分析其在各個時期的股價異常報酬是否與分群前有所不同。 研究顯示，在淨賣出時，股價在各期的宣告效果皆比淨買入時低，股價異常報酬也不會在宣告庫藏股後就由負轉正。而內部人交易為淨買入且買回股票目的為轉讓予員工時，其在宣告後的股價反應比買回股票目的為維護股東權益時大；而當內部人淨賣出且買回股票目的為維護股東權益時，股價異常報酬在宣告後第一季、第一年及第二年皆有顯著變高。由此可知，內部人淨交易情況與買回股票目的皆會對股價造成影響。 ;The purpose of the paper is to investigate whether the investor’s decision to announce a repurchase is based on the difference in the circumstances of the net insider trading and the purpose of the announcement. However, after the announcement, there is a significant difference in abnormal returns in the short and long term. Firstly, this paper divided insider trading into two groups: net buy and net sell, and extended the observation period to the third year after the announcement, and analyzed the short-term and long-term abnormal returns of the stock price of these two groups respectively. Subsequently, by grouping the above modules according to the purpose of the repurchase and to analyze whether the abnormal returns of the stock price in each period are different from those before the grouping. The research showed that the effect of the announcement of the stock price in each period was lower when there was net sell than when there was a net buy, and the abnormal return of stock price after the announcement of the treasury stock did not shift from negative to positive. In the case of an insider trading as a net buy and the purpose of the repurchase is to transfer to employees, the reaction of stock price after the announcement is greater than if the purpose of the repurchase is to maintain shareholders′ equity; In the case of insider trading as a net sell and the purpose of the repurchase is to maintain shareholders′ equity, and there was a significant increase in abnormal return of stock price after the announcement in the first quarter, first year and second year. As a result, both the net insider trading activity and the repurchase purpose have an impact on the stock price.
