本文利用1995至2004年之日內交易與報價資料及準確性之宣告時點檢驗市場對股票購回宣告之日內反應。 根據我們的樣本發現股票購回宣告具有資訊內涵，且市場具有效率性。股價在宣告訊息發布的ㄧ分鐘內上漲，交易強度增加。實際購回股票之公司具有些微較高的市場反應。投資人可在股票購回宣告前根據相關訊息交易可得到小額獲利。 宣告股票購回亦造成報價流動性的改變。包含股票購回宣告的半小時區間內，流動性下降，符合資訊不對稱假說，可觀察到價差增加、深度下降。 We use intraday trade, quote data and exact announcement times to examine the within-day pattern of the market reactions surrounding repurchase announcements. The sample period is from 1995 to 2004. We find that repurchase announcements samples have information content. The market incorporates repurchase announcements within one minute of initial release. The price response is positive and slightly stronger for firms with actual buyback. There is a significant increase in trading intensity within the event period. Investors who trade before the initial release earn small profit for compensating their effort in gathering information. Quoted liquidity varies because of the repurchase announcements. The quoted spread increases and quoted depth decrease during the event period. The liquidity is decreasing and consistent with the information asymmetry hypothesis.
