Evaluating the Effect of Asymmetric Information and Scale Effect on Market Structure in Tehran Stock Exchange

Role of information in economy started from questioning one of the assumptions of perfect competition theory in market. In stock market, information plays an important role in determining the level of competitiveness. In this study tried to measure the competitiveness of firms in Tehran Stock Exchange by using income equations in the presence of asymmetric information. In this regard, first, using the income equations and a GLS- Panel has been paid the effect of various variables. The results indicate that equations without the effect of scale offer better specification of the firms’ conditions. Although asymmetric information is high in stock market and stock gains influenced by the degree of asymmetric information, but extent of this influence is limited. The “H competitiveness index” shows that monopolistic competition is best description of market conditions in equations of incomes from changes in stock prices, but in equations of incomes from stocks dividends and accumulated, the performance of studied firms be explained with monopolistic behavior.