Journal of Economic Modeling Research

The level of asymmetric information in financial markets is important for its impact on the market formation, price levels and its interaction with investment risk. Also, determining the optimal rules by policy makers and determining the trading strategy by investors is done according to the level of information symmetry in the market. In financial literature, many metrics have been developed to measure the asymmetry of market information. In recent years, another measure known as probability of informed trading (PIN) has been introduced to measure the level of asymmetric information, based on the framework of market microstructure. Larger PINs from 0 to 1 range indicate higher information asymmetry levels. In this study, using the Easley, O'Hara (1992) approach, the probability informed trading as a measure of the level of market information asymmetry for the 12 selected companies from listed companies in Tehran Stock Exchange is estimated. We used maximum likelihood to estimate parameters with R package. The results show that average of PIN varies from 0.35 to 0.4 for different companies.

In financial markets, the symmetry of information and the homogeneous interpretation of information among traders is one of the main conditions for market efficiency, but these conditions are in fact violated. In this paper first; we accurately estimated the dynamic measures of trades stemming from information asymmetry and diverse opinions among investors indices by a hidden Markov model. Thereafter, we consider an event window of 21 days to investigate impact of information disclosure on that indices. For this purpose, we estimated the daily measures of probability of informed trading (PIN) and symmetric-order flow shock (PSOS) 32 Tehran Stock Exchange (TSE) stocks belonging to 11 industries of TSE during the period from 2015 to 2018. PIN is an indicator of asymmetric information risk and PSOS indicating diverse opinions among investors whose variations and intensity play an important role in price formation and stock liquidity. These results show that in most stocks that have higher market value experience less risks of asymmetric information and diverse opinions shocks than other stocks. Entirely, it appears that the average and the maximum of information risk and diverse opinions shocks at TSE are higher than in developed markets. Also, information disclosure decreases PIN for three days and increases PSOS for 10 days, significantly, but its impact on PIN is weaker than PSOS. Actually, in TSE, information advantage of some informed traders are independent of announcements as well as announcements causes opinion diversities to rise and stand up.