The Effects of Independent Audit Opinion on Stock Returns: Case of Borsa Istanbul

The purpose of this study is to investigate the change in the stock returns traded on the Borsa Istanbul shares market in the days surrounding the announcement of the independent audit opinions and the days around. For this purpose, 612 independent audit reports of 17 firms, which have been operating continuously in BIST-TUM index between 2009 and 2018 and published quarterly independent audit opinions, were examined. In the study, Event Study Method, Patell Z-Statistic and Standardized Cross-Sectional Test were applied. According to the results obtained from the test results (-10, + 10) in the event interval, independent audit opinions are not statistically significant on stock returns. This result shows that independent audit opinions do not affect investors' trading decisions. Therefore, Borsa Istanbul (limited by the firms used in this study) is effective in a semi-strong form.