The aim of this study is to investigate the test of stock price synchronicity on risk of stock price reduction in companies listed on the Tehran stock Exchange. In this study, financial information of 109 companies has been investigated during the period from 2010 to 2015 (654 companies-years). The compound multivariate regression has been used to test the research hypotheses. In general, the results show that the synchronicity of stock prices is an effective factor on risk of stock price reduction.Other findings of the research indicated the positive and significant effect of negative coefficient of stock return skewness and profitability index on risk of stock price reduction as well as, inverse (negative) relationship of the ratio of institutional investors’ investment and company size on the risk of stock price reduction and also, meaninglessness of relationship of growth opportunities and financial leverage with the variable of stock price reduction risk.

stock price synchronicity measures the degree to which market change can explain stock price movement, and stock price informativeness measures the degree to which information can explain this movement. The effect of information release on price is higher in optimal information environments than other environments and, as a result, informativeness is higher. In this situation, the effect of market and industry changes on stock price will be reduced, consequently reducing stock price synchronicity. Theoretically, stock price synchronicity and stock price informativeness are two sides of the same coin, but studies have shown different results. These two criteria have different behaviors in various environments based on the company’ s fundamental variables. As a result, the goal of this study was examining the role of stock price synchronicity and stock price informativeness on portfolio optimization. Thus, by collecting 300, 000 pieces of data from 130 sample companies during 10 years, we computed stock price synchronicity and stock price informativeness. Then, by analyzing these data using data envelopment analysis (DEA) and fuzzy Delphi techniques, we made several portfolios and compared them. The result demonstrated that these two criteria have different behaviors in different situations and if stock price synchronicity and stock price informativeness are considered in portfolio selection, then portfolios will have a better return. Considering stock price synchronicity improves the return of portfolio by 86% and stock price informativeness improves it up to 75%, while this value will be reduced to 47% on average without considering these crtieria.

stock price crash risk has a significant impact on investors, creditors, managers, and shareholders, so the prediction of this phenomenon is a very important issue in investment and risk management decisions. This research investigates the effect of business strategy and stock price synchronicity on stock price crash risk. Following Bentley et al. [2], composite strategy score has been used to proxy for an organization’, s business strategy, expanded market model regression following Chen et al. [3] to measure the firm-specific crash risk, and R 2 method of Johnstone [16] to calculate the stock price synchronicity. In order to achieve this point, financial information of 171 companies that are listed on Tehran stock exchange have been selected during the time period of 2013 to 2018, and data was analysed using regression model. According to the results, companies with defender (analyser and prospector) business strategy are less (more) prone to future crash risk. Moreover, results show that stock price synchronicity has positive effect on stock price crash risk, while in companies with analyser business strategy it can reduce the stock price crash risk. The interactive effect of business strategy and stock price synchronicity on stock price crash risk in companies with prospector and defender business strategy is not significant. Other findings suggest that Institutional ownership has positive, and company’, s age has negative effect on stock price crash risk.

The purpose of this research was to investigate the role of uncertainty in monetary policies on the synchronicity of company’, s stock prices. The statistical population of the research consists of all the companies listed in Tehran stock Exchange between 2010 and 2019, of which 118 companies have been studied as a statistical sample of the research. The research data were analyzed using regression models using the pooled data method. In order to measure the uncertainty in monetary policies, two methods based on the entropy of exchange rate values and also fitting the GARCH heterogeneous variance model were used. The findings of the regression models showed that the increase in uncertainty in the monetary policies of each period under both the entropy criteria and the GARCH model has an adverse effect on the synchronicity of the stock prices in the future period. Therefore, the degree of stock prices synchronicity in each period can be predicted by relying on the uncertainty of monetary policies of the past period and the company's financial ratios. Also, the results showed that managers' strategies in order to reduce the debt ratio, increase cash retention and under investment to deal with the uncertainty caused by monetary policies, have a moderating effect on the relationship between this uncertainty and price synchronicity and strengthen the size of its effect on the synchronicity of the stock prices in the future period.

Objective: Pyramidal ownership structures and cross-ownership are common phenomena in developing economies. These structures result in a divergence between voting rights and cash flow rights on the one hand, and create internal capital markets through which firms can raise capital internally instead of going to the public market when they need additional financing. In the present study, the effects of firm interlock and stock price synchronicity in Iran stock Market was investigated. Methods: We used a unique data set containing stock ownership and directors of all companies listed on the Tehran stock Exchange considering three definitions of management, stockholding, and ownership and examined interlock through both equity ties and interlocking directors. Results: We found that over 40 percent of all listed companies belong to networks of interconnected companies and there was a significantly positive relationship between being a member in each of these networks and the profitability of the firm alongside other colleagues. We also documented a complex set of networks among listed and unlisted companies, which have not been previously documented. We further find that pairwise interlocks through equity ties – either direct ownership or common owner – are correlated with higher stock price synchronicity, whereas common directorship is not linked to return co-movement. We can also claim that the effect is decreasing as firms become farther away from each other within a network. Conclusion: The results show that firm interlock, particularly through cross holdings and common ownership, can increase stock price synchronicity.

The managers tend to hoarding and accumulation of bad news for extended periods. The hoarding and accumulation of bad news for extended periods lead to stock price crashes when the accumulated hidden bad news crosses a tipping point, and thus comes out all at once. Theoretical literature shows that the main root of stock price synchronicity and stock crash risk is the lack of transparency of financial information. In this study, the relationship between stock price synchronicity and stock crash risk was investigated. Due to Limitations of the study, 63 listed firms of Tehran stock Exchange, during the period 2009 to 2014 was studied. To do so, down-to-top volatility model was applied to measure stock crash risk and Also, For data review and test of the hypothesises from panel data was used. The results showed that between stock price synchronicity and stock crash risk there was no a significant positive relationship.

The purpose of this research is to study studying the relationship between stock price synchronicity and tails of return distribution at Tehran stock Exchange. The sample consists of 118 companies that have been chosen from among compaines listed in Tehran stock Exchange during the period of 2010-2014, and hypothesis testing has been done with multiple regression based on panel data. The results of hypothesis testing show that firms with high stock price synchronicity have higher probability of generating positive tails than firms with low synchronicity, and also there is positive relation between stock price synchronicity and skewness. Investors of stocks with hig price synchronicity have lower reaction to bad news in respect to stocks with low price synchronicity. High stock price synchronicity show that market information reflected on stock return is more, and investors suffer only systematic risk. Therefore, it is suggested that investors in Tehran stock Exchange invest on stocks with higher stock price synchronicity and with higher information transparency.

The purpose of this research is to determine the effect of financial statements comparability as one of the qualitative characteristics of financial reporting on stock price synchronicity. stock price synchronicity is a criterion that has been used inversely to measure the information content of stock prices. In order to attain the research purpose, 86 companies among the listed companies in Tehran stock Exchange during the years 1385 to 1392 (2007-2014) were selected as statistical samples. For analyzing data and testing hypotheses, multi variable regression model with compound data and mean comparison test have been used. Findings of research signify that financial statement comparability has a significant negative impact on stock price synchronicity. The results also show that in firms with lower synchronicity, information asymmetryis lower. Based on this finding, it can be concluded that financial statements comparability causes the higher level of firm-specific information to be reflected in stock prices.

In recent decades phenomena based on inefficiency have been observed in various international stock exchange markets. The phenomena such as extreme fluctuations in prices, price bubbles, falling price, calendar effects, differences in the return on stocks of small and large companies, and the difference in return on equity and growth, all reflect market inefficiencies and the absence of a balance between price and fundamental variables. It is anticipated that the synchronization of stock prices and the risk of falling stock prices would have an effect as well as herding behavior as a mediator on the relationship of this variable. The sample companies in this study belong to the companies accepted in the Tehran stock Exchange in the period from 2012 to 2016. In this study Chen et al. (2001) and Kim et al. (2011) models for stock price crash risk and Piotroski and Roulstone (2004) models for measuring the stock price synchronicity and Lakonishok model (1992) to measure herding behavior. The findings show that there is no significant relationship between stock price synchronicity and the stock price crash risk, the result of the second hypothesis of the research is based on the mediating role of herding behavior in the relationship between stock price synchronicity and stock price crash risk.

stock price synchronicity is a relative measure of companyspecific information in comparison with the market and industry data that is reflected in stock prices; therefore, it is inverse to transparency. The purpose of this paper is to investigate the effect of managerial optimism on stock price synchronicity. To achieve this goal, the satistical sample of this study consists of 112 firms listed on the Tehran stock Exchange during 2010-2016. The Piotroski & Roulstone's model (2005) was used to measure stock price synchronicity and managerial optimism has been measured based on three criteria including accuracy of profit prediction by managers, the surplus of capital expenditures, and the remainder of the company’ s growth model. The findings showed that optimism (surplus capital expenditures) has a positive and significant effect on synchronization. But There was no significant effect on the other two optimistic proxies.