سجاد بهپور

This paper studied the impact of the most important factors affecting on volatility of GDP in Iran by using Dynamic Stochastic General Equilibrium (DSGE). Furthermore, it is important to understand the contribution of each of the factors to create volatility in GDP. To this end, we introduced institutional quality in production function. In our model, oil price shock is assumed to affect macroeconomics variables through affecting on productivity. The paper applied the model in Iran economy for the period of 1989-2014. The results indicated that one structural break had taken place in GDP in 2007:3 and Gross domestic product volatility has increased in the period after the structural break. The reason for this structural break can be found in the rise in oil prices that began in 2004 and continued for several consecutive years. We also found that the share of factors that affect volatility in GDP has changed after structural break. The variance decomposition indicates that volatility in GDP is most affected by the oil price and the monetary policy shocks. Besides, their share increases after the break point. The share of oil price shocks before the structural break was about 28 percent, but the share rose to 35 percent after the structural break.

In the economic literature, there is no specific relationship between advertising costs and firm growth, and conflicting results have been observed in empirical studies. This paper examines the impact of firm size and advertising expenditures on the growth of food and beverage industry firms during the period of 1977-2007 in Iran. Model estimation using panel data and constant effects method indicates that advertising has a positive and significant effect on firm growth. The results also indicate that the firm's growth rate is independent of firm size at the beginning of the period.

Decision making requires information and managers are always confronted with the problem of which information investors need for decision making. Every decision maker has a framework for his decision making based on his own mental structure; he encounters issues regarding his decision making framework as Stamp reports that one of the major difficulties in accounting standards development is lack of knowledge of decision making nature and logical process which decision maker attempts to access. The firm’s rate of return on investment is one of the main decision making criteria for investors and rate of return on investment calculation as a criterion for firm performance evaluation is obtained from information disclosed by the firm management. Cases of studies on information disclosure is summarized in the following pat; so it is concluded which information should be reflected in financial reports and how people process information for achieving their prediction and decision making regarding future uncertain events. Sing-Vey and Desay (1971) performed a research titled as ‘experimental quality analysis of financial disclosure by firms’ in USA. They argue that information disclosure by the firms may be in various forms and annual report to stockholders is an important form of periodical disclosure. They found that: Disclosure quality is better in large firms compared to smaller ones. Disclosure quality is better in the firms with higher number of stockholders. Disclosure quality is better in the firms audited by CPA institutes compared to the firms audited by small institutes. In the studies, there is a duality relationship between disclosure quality and stock return. While some studies have examined the effects of disclosure quality on stock return, other studies have examined the effects of stock return on disclosure quality. Reviewing the evidence of the validity of both approaches mentioned above, can mean that there is a bilateral (two-sided) relationship between these two variables. Accordingly the above question is raised: “Is there a bilateral relationship between disclosure quality and stock return?” In this regard, the goal of the present research is to study the bilateral relationship between disclosure quality and stock return in 127 listed companies of Tehran Stock Exchange (TSE) during 2003 to 2011. Research Hypotheses Based on the theoretical literature and the conducted studies, research hypotheses were developed as follows. First main hypothesis: There is a bilateral Significant relationship between disclosure quality and stock return The research methodology is a quantitative research that uses the scientific method and empirical evidence, and based on hypotheses and research designs has been set. This category of research is used when that criteria for measurement data quantitative and statistical techniques are used to derive the results. In this research, data of 127 companies are analyzed for the period of 2003-2011. At first, the bilateral relationship between the two variables was confirmed with granger causality test; then simultaneous equations system was estimated using two-step regression. The related data was collected through observation of Iranian database of Tehran Stock Exchange (Tadbir Pardaz) annual data files and the accompanying notes as found on www.rdis.com. For statistical analysis and to test hypotheses, descriptive statistics (i.e., mean, maximum, minimum and standard deviation) and inferential are used. The collected data was calculated using the Excel software and was analyzed using Eviews-7. The results of this research show that at a confidence level of 95%, there is bilateral relationship between disclosure quality and stock return of listed companies of TSE. In other words, the results of the simultaneous equation system have more reliability and validity than single-equation. Discussion and Financial information forms the evaluation basis in capital market. Financial statements contain very important information that shareholders use in making decisions related to investments in stocks. Appropriate disclosure in financial statements will be helpful in the decision extent that provides the possibility of predicting earnings trends, continuing profitability, management performance and so on. While some studies have examined the effects of disclosure quality on stock return, other studies have examined the effects of stock return on disclosure quality. The goal of present research was to study the bilateral relationship between disclosure quality and stock return in listed companies of TSE. It is recommended to encourage the companies having high-quality disclosures and charge the companies that have low-quality information disclosure given the importance of the quality of information disclosure on the exchange market. Thus, the regulators can affect the quality information disclosure (such as resource allocation in the economy and efficiency of information). Also, according to the bilateral relationship between stock returns and disclosure quality, we suggest considering these findings’ order to disclosure levels.

The goal of present research is to investigating the Non-Linear relationship between growth and profitability of the companies listed in tehran stock exchange (TSE). In this regard, the effects of firm size, financial leverage and liquidity ratio have been controlled either. Statistical society of present study consists of 173 listed companies of Tehran Stock Exchange during 2003 to 2011. First, after examing the literatures, which has confirmed the nonlinear relationship between growth and corporate profitability, this stydy attempted to assess the reliability of data using Levin, Lin and Chow Test, And then nonlinear relationship using Eviews software is estimated. Analysis results express that, there is a significant non-linear relationship between growth and corporate profitability, That coincided with the growth of the company, Its profitability increases, but this relationship has a threshold exists, and from that point onwards, with increse of the company grows in any amount, its profitability is reduced.

In order to estimate the production function besides productivity and economic growth, the time series of capital stock is required. Time-series that available for capital stock is not so reliable because of Variations in suggested methods and also difficulty in the calculation of this variable. The continuously inventory method (CIM) has been more attention, among the existing methods. We improve CIM in this research. For estimating the capital stock we developed an algorithm and titled that “Programming or Recursive Algorithm”.The following can be noted in capabilities of the model that developed in this study. Unlike the previous studies we taking the variable depreciation rate of capital in different periods, considering the quality variable of war and its impact on the rate of depreciation, investigation of nonlinear and linear production function in order to increase estimation accuracy and considering energy as well as labor and capital input.The results show that compared to the time series reported by the Central Bank of Iran, the series calculated in this study are similar trend, but with some differences.The mean of depreciation rate has been calculated 5.1% for the period 2009 to 2010. The estimation results show that in war period we have always higher depreciation rate than average rate of depreciation in period of this study.

Many studies in the economic literature have devoted to analysis the effect of economic freedom on the economic growth and income per capita، but less study have analyzed the effect of economic freedom on the economic fluctuations. This Study has analyzed the effect of economic freedom on the economic fluctuations for 48 developing countries over the time period 2000-2010. To measure economic fluctuations two indices، “standard deviation of GDP growth” and “GDP fluctuations”، and for economic freedom “Fraser Institute Index” have been used. Models estimation has done by using cross section and panel data and results show that an increase in the economic freedom index reduces economic fluctuations.

The so far studies، reveal a dual relationship between disclosure quality and firm performance. While some studies have examined the effects of disclosure quality on firm performance، other studies have examined the effects of firm performance on disclosure quality. Reviewing the evidence of the validity of both approaches means that there is a bilateral (two-sided) relationship between these two variables. In this regard، the goal of present research is to study the bilateral relationship between disclosure quality and performance of 149 companies listed on Tehran Stock Exchange (TSE) during 2004 to 2010. At first، the bilateral relationship between two variables was confirmed using Granger causality test and then simultaneous equations system was estimated using two-step regression. Based on the results، there is bilateral relationship between disclosure quality and performance of the companies listed on the TSE. In other words، the results of the simultaneous equation system have more reliability and validity compared to single-equation system.

Simultaneous variations between world oil price and food prices leads to stimuli scientists to investigate the effect of raising oil price on food prices. The main purpose of this paper is to examine the effect of oil price volatilities on the food price index for the 1990-2006 periods in Iran. To achieve this goal، a vector auto-regression (VAR) model، impulse response function and a auto-regressive distributed lags (ARDL) model have used. The results of impulse response function show that oil price volatilities have no effect on food prices in Iran.. Moreover، results from ARDL model implies that there is no significant relationship between oil price and food prices in the short term and long term. This result may be due to subsidies paid by the government to energy section that prevent any price changes.

There is a duality in studies on the relationship between growth and firm profitability. While some studies have examined the effects of growth on firm profitability، other studies have examined the effects of firm profitability on growth. Reviewing the evidence of the validity of both approaches mentioned above can mean that there is a bilateral (two-sided) relationship between these two variables. In this regard، the goal of present research is to study the bilateral relationship between growth and firm profitability in 173 companies listed in Tehran Stock Exchange (TSE) during 2003 to 2011. First، the bilateral relationship between the two variables was confirmed with Granger causality test and then simultaneous equations system was estimated using two-stage regression. The results express that there is a bilateral relationship between growth and firm profitability of listed companies of TSE. In other words، the results of the simultaneous equation system are more reliable and valid than that of single-equation.

This study examines the relationship between unemployment and productivity growth in Iran over the time period 1359-1389 (1980-2010). Recently، studies on this relationship have had different and sometimes opposite results. We have examined the relationship between the growth rate of productivity and the rate of unemployment by using Granger Causality test and Hausman Test in the estimation of simultaneous equations. Our results show a bilateral causal relationship between these two variables; that is، the increase in productivity cause the rate of unemployment to decrease and the decrease in the rate of unemployment cause productivity to increase، a result in line with learning by doing effect.