Tail Risk and Excess Stock Returns: Evidence of Momentum and Idiosyncratic Risk Anomalies

Capital market anomalies are caused by factors that have not been considered in capital asset pricing models. One of the arguments for explaining anomalies is the theory of extreme value. According to the theory of extreme value, tail risk is an adverse event that can have a negative impact on excess stock returns. Therefore, the aim of the present study was to investigate the effect of combining momentum anomalies and idiosyncratic risk with tail risk on excess stock returns. In the present study, two criteria of cumulative tail risk and combined covariance tail risk have been used to calculate tail risk. The sampling method in this study is systematic elimination and the time period of the research years from 2007 to 2019 has been selected. The number of sample companies includes 136 companies listed on the Tehran Stock Exchange (TSE) and the 5-factor regression of Fama and French was used to test the research hypotheses. The results indicate that the combination of idiosyncratic risk portfolio and tail risk has a positive and significant effect on excess stock returns. Therefore, by combining this portfolio, investors can gain returns in the Iranian capital market. Also, the results showed that the combination of momentum portfolio and tail risk does not lead to excess stock returns. In general, the results showed that tail risk can be used to explain the existence of idiosyncratic risk anomalies.