Evaluation of Shareholders’ Overreaction and its Comparison in Small and Large Companies (Case Study: Accepted Companies in Tehran Stock Exchange)

Overreaction is one of the anomalies in stock market that has a destructive effect on market efficiency. The purpose of this article is to assess the overreaction of shareholders and comparison this phenomenon in small and large companies in Tehran stock exchange. Also, in this research we evaluate the performance of contrarian investment strategy to achieve abnormal returns. The study period was from 1382 to 1396. We used the De Bondt-Thaler winner–loser effect method to assessing the overreaction phenomena. The results showed that an overreaction exists among the shareholders of Tehran stock exchange. Also, the overreaction has been observed among the shareholders of large companies; but it hasn’t been observed among the shareholders of small companies. Generally, investors and portfolio managers can take advantage of market inefficiencies and to achieve abnormal returns by following a contrarian strategy in Tehran stock exchange.