早期的購併股價績效研究，多以短期CAR模型作為衡量方式，但購併行為的促成與否，多以長期是否有綜效的出現來決定。故本研究以短期與長期股價績效衡量之結果，來看市場是否可以真實在購併當下反映出購併兩至三年後的價值，發現(1)購併股價績效以短期方式衡量都沒有異常報酬的出現，顯示市場並不預期購併對於主併公司會出現綜效或損失，所以股價並沒有異常報酬；(2)以長期方式衡量，則會因使用的模型不同而使結果出現分歧，全體、非金融、相關樣本長期績效以AMAR及BHAR模型衡量，會出現負向異常報酬，顯示市場不能在購併當時立即股價反應購併價值；以三因子模型衡量，卻顯示無異常報酬，可能原因為其與AMAR、BHAR模型在選取預期報酬的標準不同導致。(3)金融樣本則是在長、短期都不會出現異常報酬，表示金融業購併沒有綜效出現，且此一事實會立刻被市場反應。(4)非相關樣本在長期績效的衡量上以三種不同模型會得到三種不同結果，無法確實區分出其長期績效為何。(5)綜效動機下的購併行動以長期方式檢測有負向異常報酬，而短期則無，可能是因為在分群時被資訊誤導，自傲假設或代理人問題的購併行動被誤判為綜效動機，導致長期市場發現沒有綜效而調整股價，使股價下跌。(6)非綜效動機下的購併樣本，以長、短期方式檢測都無異常報酬，表示在購併宣告時，市場已經認為將來該購併不會有綜效出現，因此股價沒有異常反應，而長期觀之，市場也確實沒有異常報酬的產生，完全依照市場機制的運行。

關鍵字：購併、長期績效、短期股價績效、市場反應

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