Özet:

The purpose of this study is to examine the impact of announced financial news via the Public Disclosure Platform on the BIST -30 traded companies’ stock performances. The study will also investigate whether the market is semi- strong form efficient. For the data analysis event study is used. As a result of calculations, it is determined that investors mostly react to the ratings by ratings agencies and debt news at the day of event. It shows that existence of abnormal returns before disclosure, market is not efficient at semi-efficient form in terms of market efficiency. Besides, all average cumulative abnormal returns are positive and statistically significant and this can be taken as a suspicion of insider trading.

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