Investigating the effect of herd behavior in the Iranian economy on the efficiency criteria of the asset pricing model

The capital asset pricing model provides an equilibrium model to show the relationship between risk and return on assets. One of the economic areas is herd behavior, which has attracted a lot of attention in recent decades. Therefore, the present study deals with the herd behavior in the Iranian economy on the efficiency criteria of the asset pricing model. The research method used in this research is correlational research that a regression method has been used to test the research questions. To test the hypotheses, Karhart's 4-factor model was used, to which the bulking factor was added. The statistical sample of the present study includes 115 companies active in the Iranian economy. The research period is for 10 years, which has been studied from 1389 to 1398. The results show that mass rotation is different in different degrees of risk and occurs more in high risk areas of the market and causes a return of beta in the market and the inefficiency of the capital asset pricing model to is following. It was also found that by removing high-risk portfolios from the sample, no bulkiness is observed and beta behavior is stabilized according to the theory of capital asset pricing model and beta return does not occur.