The effects of independent audit opinion on stock returns: Case of Borsa İstanbul

The purpose of the thesis is to measure the impact of independent audit opinion on the market and stock returns at Borsa Istanbul (BIST) during the dates the opinions are issued and the days that followed them. The thesis investigates 612 independent audit reports by 17 audit companies who have been continuously active at BIST-TUM index from 2009 to 2018 and who have issued independent audit opinions every three months. The study's methodological inventory includes Event Study, Patell Z-Statistic and Standardized Cross-Sectional Tests. According to findings of tests, in a scale of (-10, +10), independent audit opinion has no statistical significant effect on stock returns and don't affect stock returns and consequently, investors' stock buy and sell decisions.. In other words, Borsa İstanbul (limited by the firms used in this study) is effective in a semi-strong form.