Evaluating Efficiency of Tehran Stock Exchange: Case Study for Top Fifty Most Active Companies (TSE-50)

Economics of information has been developing increasingly in economics literature in recent decades. Accordingly, the information plays a crucial role in efficiency of any market particularly capital market which deals more with this issue. As for the importance of information in stock exchange efficiency, the market efficiency is studied under three data sets in three forms including: 1- Information concerning the past prices, 2- All the released information and, 3- General Information and Confidential private information. Given these three types of information, market efficiency is checked in three weak, semi-strong and strong levels, respectively. This paper in order to examine the efficiency in the weak level employs a decomposed pattern with two stochastic and random terms for Top Fifty most active companies (TSE-50) in Tehran stock exchange based on both long and short horizons. The findings demonstrate that the indicator does not have efficiency in long horizon. This is while; the efficiency is verified in short horizon.