| Summary: | 碩士 === 國立政治大學 === 財務管理研究所 === 105 === This paper examines the effects of Taiwan mid-cap 100 index revision and news coverage on stock price and volume. Using event study method, the sample of this study is divided into four groups: pure additions, downward additions, pure deletions, upward deletions to analyze the changes of stock prices and volume on the announcement day and effective day. Furthermore, the effects of news coverage between announcement day and effective day are also investigated. Results of our analysis suggests that there are significantly positive (negative) abnormal returns (ARs) for pure additions (deletions) on announcement day and the day before effective day but transitory. For downward additions and upward deletions, there are significantly negative ARs for the former and significantly positive ARs for the latter. However, both ARs reverse within five days. Besides, there are abnormal volumes in the entire sample. As for the effects of news coverage, pure additions (deletions) are divided into two groups to examine the existence of ARs, one group with bullish (bearish) news and one group without. Results show that pure additions (deletions) with bullish (bearish) news have higher ARs than those without news coverage, supporting our hypothesis that in the event of index revision, news coverage do affect stock prices
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