Collective Behavior

Banked based financial sector of Iran leads us to focus on the banking industry and its components. One of the important aspects of this industry is its coupling structure. In this paper, we have analyzed the collective behavior of Iran banking sector by Random Matrix Approach (RMT). This technique is useful for splitting the information part of the correlation matrix from the random region. This research confirms good compliance with random matrix predictions. By removing the market mode of the system the average of the banking cross-correlation matrix changes. Then, by calculation of the participation ratio, node participation ratio and relative participation ratios of these banks, it is shown that the collective behavior of the system is so fragile. Also, by applying local and global perturbations on the banking sector, it is shown that this system is very sensitive to the global perturbation and the mean value of cross-correlations decreases rapidly that means some banks have crucial effects in the market. 

Many behavioral biases affect investors when making decisions.Behavioral distortions divert the investor from rational decisions, and as a result, resources are not diverted to appropriate investments.Behavioral biases can be evaluated in different types including the two phenomena of mental anchor and collective behavior of investors. In the present study, the phenomenon of collective behavior and mental anchor of investors with emphasis on significant weaknesses in internal control has been investigated. For this purpose, the data of 125 companies listed on the Tehran Stock Exchange during the period 2012 to 2018 were used.Data analysis was performed in eviews software version 10 and in order to fit the regression models,the generalized least squares method of panel data was used. The results using univariate analysis showed that there is no significant difference between the amount of behavioral biases in each of the two groups of companies with weakness and lack of weakness in internal control.While multivariate analysis of data in the form of regression models showed that the auditor's report on significant weaknesses in internal control,(which Weakness indicates high agency costs and high information asymmetry between managers and shareholders) strengthens It is the collective behavior of investors but it has no effect on their mental anchor.According to the results, it seems that the behavioral biases of investors are conditioned by the priority and importance of good and bad news in the market.As long as there is bad news in the stock market towards the company, good news can’t cause behavioral bias in investors.