Rumors

In this research, the impact of clear rumor declarations on the measurement of abnormal stock returns behavior has been investigated in Tehran Stock Market by means of event research so that to reveal well abnormal stock returns behavior. Following testing 169 clear rumor declarations during the period (2017-2019), Using Spss statistical software version 26 and Eviews version 12, the results of regression analysis and correlation tests indicate that content of clear rumor declarations may affect abnormal stock returns behavior. Confirmation of good rumors has increased the efficiency of abnormal stock returns 10 days after the date of the given declaration and approval of bad rumors has led to reducing the efficiency of abnormal stock returns upon declaration day. Similarly, the results showed that if rumors were disclosed during working hours in Tehran Stock Market they would reduce the efficiency of abnormal stock returns on the same day. After comparing the results of the research, the need to educate and promote the shareholding culture among shareholders is felt more than ever before. They also need to shift their focus from focusing on rumors to principled investing in futures stocks to avoid cross-sectional fluctuations, destructive rumors and other market risks and achieve a good return stock