台灣於民國89年8月9日正式實施庫藏股制度，至此以後公司管理當局可以選擇透過發放現金股利的方式，或是以股票購回方式將公司現金分配給股東。
本研究以股票購回公司與現金股利政策變動公司為研究對象，探究兩大研究主題，首先比較股票購回宣告與現金股利增發宣告之宣告效果，而後再探討股票購回對現金股利變動宣告效果的影響。
實證結果發現，公司在進行股票購回宣告前股價有下跌的現象，在進行股票購回宣告後股價有顯著的異常報酬。而現金股利增發公司，在進行現金股利增發宣告前股價則有上升的現象，在進行現金股利增發宣告後四日內股價異常報酬率顯著為正。經由統計分析結果發現，市場對於公司進行股票購回宣告的反應大於對現金股利增發宣告之反應，股票購回比現金股利增發能為股東帶來較大財富。
在股票購回對股利政策變動宣告效果之影響方面，比較有無進行股票購回公司的現金股利變動宣告效果，研究結果發現，股票購回會增強公司現金股利增發的正面宣告效果，也會減弱公司現金股利減發的負面宣告效果。因此，本研究認為股票購回宣告對公司現金股利政策變動的宣告效果有正面影響。

Share repurchase system has been formally implemented in Taiwan since August, 9, 2000. When a company decides to payout, it can choose either cash dividend or stock repurchase.
This paper will study the effect of both stock repurchase and cash dividend announcement first. Secondly, it will continue to study the impact of stock repurchase on cash dividend announcement.
As the empirical result shows, stock price will come down before firms announce stock repurchase. Stock price will bound up after firms announce stock repurchase. As for companies which choose to pay cash dividend, their stock price will rise before firms announce to increase cash dividend. And after cash dividend announcement, its stock abnormal return will apparently be positive. Market reacts to a company’s stock repurchase announcement will be larger than its dividend announcement, which shows that stock repurchase announcement can bring more profits to shareholders than dividend announcement.
In the impact of stock repurchase on the effect of cash dividend announcement, by comparing companies those have repurchased stock and those have not, the result shows that stock repurchase will strengthen the positive result of dividend increased and reduce the negative impact of dividend of dividend decreased. Hence, this paper shows that stock repurchase announcement has positive impact on the effect of cash dividend announcement.

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