本研究針對2016年至2020年間,曾被納入(或被剔除)至臺灣公司治理100與櫃買公司治理指數之台灣上市(櫃)公司為樣本,利用事件研究法分別檢定納入日(或剔除日)前後10個交易日之普通股股價變化。 研究結果顯示樣本股價會隨著不同指數、新增或剔除,以及電子業或非電子業產生不同之反應程度與方向。對新增納入指數樣本而言,當上市公司被納入至台灣公司治理100指數,其納入日前存在顯著的正向異常反應,但是相反當上櫃公司被納入至櫃買公司治理指數時,其股價卻是產生顯著負向反應。至於,對被剔除在外樣本而言,自台灣公司治理100指數被剔除之電子業子樣本股價在剔除日前後存在顯著的正向反應;相反被剔除之非電子業子樣本股價在剔除日後存在負向反應。而當上櫃公司自櫃買公司治理指數被剔除時,其剔除日前後卻是產生正向異常報酬,但非電子業子樣本在剔除日前股價雖呈現正向反應,但在剔除日後股價反轉出現負向反應。
This study selects the listed companies which have been added to or deleted from the TWSE Corporate Governance 100 Index and the TPEx Corporate Governance Index from 2016 to 2020 as samples. The event study method is used to investigate the price changes of their common stock in the 10 trading days before and after the date of addition (or deletion). The findings indicate that the sampled stock prices react to various factors, including different indexes, addition or deletion, and whether they belong to electronics industry or not. When companies are added to the TWSE Corporate Governance 100 Index, there is a significant positive abnormal effect before the date of addition. In contrast, there is a significant negative abnormal effect when companies are added to the TPEx Corporate Governance Index. When the subsample of electronics companies are deleted from the TWSE Corporate Governance 100 Index, there is a significant positive abnormal effect before and after the date of deletion. However, the non-electronics subsample has a significant negative abnormal effect after the date of deletion. When companies are deleted from the TPEx Corporate Governance Index, there is a positive abnormal effect before and after the date of deletion. However, the non-electronics subsample has a positive abnormal effect before the date of deletion and has a negative abnormal effect after the date of deletion.