內部人資訊、內部人交易與股票買回宣告效果

Insider Information, Insider Trading and Stock Repurchase Announcement Effect

本文旨在探討公司內部人在股票買回宣告前之持股交易對股票買回宣告股價反應的影響。股市投資人對於公司股票買回的原因及實際執行情況在公司買回宣告時均無法進行確認，因此股票買回宣告對股市投資人而言存有極大的不確定性。內部人成員在股票買回宣告前之持股交易反應了內部人成員之私有資訊，因此市場參與者應可透過不同的內部人成員之交易資訊評估公司買回宣告之可信度。將內部人依其性質區分成不同的成員後，發現非法人董事較法人董事之持股交易有較大之資訊內涵；財務與會計主管較其他經理之持股交易有較大之資訊內涵。值得注意的是，研究結果並未發現董事兼總經理或全職總經理之持股交易具有資訊內涵。這樣的結果意味內部人成員持股交易之動機可能大不相同，且與內部人的位階無直接關係。

This study examines the effect of insiders’ trading prior to repurchase programs on market reactions to shares repurchase announcements. Given the noncommittal nature of shares repurchase program, the extent and timing of actual repurchases are highly uncertain. Under this scenario, insiders’ trading before shares repurchase announcement may reflect insiders’ superior information over market participants. To mitigate the degree of uncertainty, this study argues that market participants probably could use information conveyed from insiders’ trading to assess the credibility of stock repurchase announcements. To investigate this research inquiry, we categorize insiders’ trading in accordance with their characteristics and find that trading from the non-legal person directors reveals more information content than those from the legal person directors. Moreover, trading from CFOs reveals more information content than those from other managerial personnel. This study does not find trading from CEO-director or CEO contains more information than those from other insiders. Overall, the results from this study imply that insiders may have different incentives to trade, based on their superior information, prior to shares repurchase announcements. However, these incentives may not be associated with their positions in a firm’s hierarchy.