This study investigates the motives behind share repurchase by examining the operating performance of firms in the literature related to this issue. However, a consensus on the effectiveness of share repurchase has yet to be reached: outperformance, underperformance, and maintenance of the operating performance of repurchasing firms have been observed. Thus, from this perspective, the motives behind repurchase remain unclear. Unlike previous studies examining return-on-assets, this paper uses total factor productivity, an important measure for operating performance in economics, to test the signaling against free cash flow disgorgement explanation. Our results suggest that the total factor productivity of repurchasing firms improves following the announcement date. Consequently, our results are more consistent with the signaling hypothesis in which a share repurchase program conveys information regarding the improved prospects of the firm. 過去財務領域文獻裡，學者利用公司購回庫藏股之後的營運績效指標，探討庫藏股宣告的動機究竟為何。先前學者研究庫藏股宣告公司的資產報酬率，並測試訊息釋放假說（signaling hypothesis）和自由現金流量假說（free cash flow hypothesis）何者為真。然而，這些文章並無法得出一致性的結論。本文利用經濟文獻常用的另一個營運績效指標：總和要素生產力（total factor productivity），研究美國上市公司宣告購回庫藏股後的生產力變化。研究結果發現，總和要素生產力在公司購回庫藏股之後有顯著的提升，表示公司宣告庫藏股的目的為釋放公司未來營運績效提升的正面訊息，這與訊息釋放假說一致。
