The Momentum Effect in the Tehran Stock Market: Risk Hypothesis vs. Under-reaction Hypothesis

The purpose of this research is to investigate two controversial cases about the momentum in the Tehran Stock Exchange. These two cases include risk theory and under-reaction theory. This research will be followed in two parts. The first part tries to explain the momentum with respect to risk. The second part describes the excess return in momentum portfolios with the under-reaction hypothesis. The research hypotheses have been examined using the data of 58 non-financial companies from the Tehran Stock Exchange between 1389 and 1398. The results show that the risk-adjusted momentum profit is statistically significant. In addition, the results show that the five-factor risk model is not able to explain the momentum effect. However, the momentum effect can be explained by using the under-reaction hypothesis. The under-reaction is asymmetric for first six month after the earning announcement date. In general, the findings also rejects the efficient market hypothesis in favor of the under-reaction theory.