我國上市(櫃)公司併購後長期績效之實證研究

Abstract

本研究係對我國1999年至2003年間，曾從事併購宣告且完成併購活動之上市（櫃）主併公司，同時研究其併購後的長期股票報酬績效及長期經營績效，主要探討以下兩點： 一、 我國主併公司，在併購後三年股票報酬績效。探討主併公司在併購後的股票異常報酬水準，和併購前是否有差異。 二、 以EVA為經營績效衡量指標，探究我國主併公司，在併購後三年經營績效。探討主併公司在併購後的經營績效，和併購前是否有差異。 本研究採用Fama et. al. (1969) 提出的累計平均異常報酬（CAR），來衡量併購後股票的異常報酬，考慮到波動聚集的現象，因此同時採市場模式的OLS及GARCH估計預期報酬；以Stern Stewart & Co 提出的EVA衡量主併公司併購後的經營績效，並採用Healy, Palepu, and Ruback (1992) 研究相同的精神，以EVA/IC作為衡量併購後績效的指標之一。 實證結果顯示，電子業主併公司於合併宣告後第271-520天及第521-770天皆有顯著的負向異常報酬，因此在併購後的股票報酬績效較併購前差；非電子業樣本公司不論以OLS或GARCH估計預期股票報酬，併購後則皆無顯著股票異常報酬，因此在併購後的股票報酬和併購前並無顯著差異。此外，對於本研究的電子業及非電子業樣本，使用OLS或GARCH模型估計期望報酬，皆會得到一樣的結果，並沒有產生明顯的差異。 以EVA衡量經營績效並沒有明顯的結果：OLS下電子業主併公司併購後第一年有顯著的負差異；非電子業樣本併購後第三年的EVA較併購前的平均EVA，有顯著的負差異。若採EVA/IC衡量主併公司併購後的經營績效，則電子業主併公司，無論以OLS或GARCH估計 ，結果皆顯示在併購後的第一到三年經營績效下滑；非電子業無論以OLS或GARCH估計 ，在併購後的一到三年皆無顯著的差異。

This study examines the long-run stock-price performance and operating performances of those publicly traded Taiwan companies undergoing mergers and acquisitions during 1999 to 2003. We focus on the following two issues: 1. The postmerger three-year stock-price performances of the acquiring firms. Examine whether the abnormal stock returns of the acquiring firms after M&A are different from premerger ones. 2. Use EVA to measure the postmerger three-year operating performances of the acquiring firms. Examine whether the operating performances of the acquiring firms after M&A are different from premerger ones. We measure the postmerger stock-price performances using cumulative average abnormal return（CAR）developed by Fama et. al.(1969). We take the effect of volatility cluster in consideration, so we use both OLS and GARCH to estimate the expected returns. We measure the postmerger operating performances using Economic Value Added（EVA） developed by Stern Stewart & Co. Besides, we also use EVA/IC to measure the postmerger operating performance in the spirits of Healy, Palepu, and Ruback (1992). The main empirical findings are summarized as follows: The postmerger stock-price performances of electronic companies are significant negative abnormal returns over the 271-520 and 521-770 day period following the M&A announcement, which means the abnormal stock returns of the electronic acquiring firms after M&A are worse than premerger ones. Non- electronic companies have no significant abnormal returns both in OLS and GARCH method, which means the abnormal stock returns of the non-electronic acquiring firms after M&A are not different from premerger ones. Besides, we also find that using OLS and GARCH to estimate the expected returns will result in the same outcomes of the abnormal stock returns. There is no significant finding in using EVA to measure the postmerger operating performances of the acquiring firms: Using OLS to estimate Beta, the-first-year postmerger EVA of electronic companies shows significant negative differences from premerger ones; the-third-year postmerger EVA of non-electronic companies shows significant negative differences from premerger ones. Using EVA/IC to measure the three-year postmerger operating performance, we find that electronic companies show significant negative differences from premerger ones both in using OLS and GARCH to estimate ; non-electronic companies show no significant differences from premerger ones both in using OLS and GARCH to estimate Beta.