The impact of environmental news on stock prices of companies listed in Tehran Stock Exchange

In this study, the behavior of investors and the stock price have been paid to the environmental news and investor's reaction is studied to the favorable and unfavorable news. For this purpose, the standard methodology of events (event study) is used. The range of events includes 11 days (5 days before to five days after the announcement) has been considered. The research population, firms listed in the Tehran Stock Exchange is between the years 2010 to 2016. Abnormal returns are calculated according to market-adjusted return. The results show, that positive environmental news boosts stock prices and positive reaction of investors but negative environmental news release impact on stock prices, and investors also associated with lack of response. On the other hand, when good environmental news is released, the investor’s interest increase to buy stocks. But when bad environmental news is released, 11-day period, It does not impact on stock price and confirms the Sullivan(2016) theory which says committed investors to social responsibility show a positive reaction to good environmental news of firms.