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This paper develops a New Keynesian dynamic stochastic general equilibrium (DSDE) model to study Iran's economy. The model considers the dependence of Iran's economy to oil exports. Oil sector and oil export revenues have been modeled as a separate sector and one of the government budget resources, respectively. In this model, like in other New Keynesian DSGE models, firms face nominal rigidities and the intermediate-good sector is monopolistically competitive. Four shocks (productivity, oil revenues, money growth rate and government expenditure) have been introduced as the sources of volatility. The findings show that business cycle moments generated by the model and those of actual statistics from the economy are closely related. The model produces more volatile private investment and less volatile private consumption than non-oil output. Impulse response functions of shocks show that non-oil output increases in response to productivity, oil revenues, money growth rate and government expenditure shocks. Although non-oil output increases in response to government expenditures shocks, crowding- out effect of these expenditures causes output to decrease after some periods.

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In macroeconomics literature inspired by traditional economists, it is said that economic growth and more equal distribution in income, are two opposite targets since moving toward more equality of income, will reduce propensity to saving. Based on the optimum growths models, it seems that the highest levels of growth can happen in a system just when in allocating the resources among the generations the attention is more paid to the concept of justice. If in this process the attention is more paid to the present generation compared to the future ones, the available resources for the whole system will decrease and as a result the economic growth will be stabilized at far lower rates. The more economic justice means the higher rate for economic growth. In this paper we use an optimal growth theory for studying the mechanics of this regularity. Empirical calibration of the model to the Iranian economy reveals that if economic policy makers in a planning period via a scenario can decrease social time preference to a 5%, real per capita GDP, consumption, saving and per capita capital formation will increase by 6.5%, 2.2% and 42% respectively.

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Fluctuations in fiscal policy affect monetary policy and the central bank, because the government’s general budget is highly dependent on oil prices and its fluctuations. Therefore, this paper designs a New Keynesian model for Iran with nominal rigidities (prices and wages) and analyzes the impact of technology, oil price, government spending and money supply shocks on macroeconomic variables (inflation, output) in economy of Iran. The data in this article are related to the fixed prices in the year 2004 and run annually from 1966 to 2008 on a per capita basis. Having logarithms taken, the variables are de-traded through Hodrick - Prescott filter. The final model equations are linearized around the steady state and using Uhlig (1999) approach, accidental equations are also linearized and are specified as space state pattern in Matlab software. Finally, the calibration of parameters are assessed, variables are simulated and compared with real data. The results show that the recommended model can simulate the impact of shocks on macroeconomic variables. It also shows that inflation rises in response to all shocks except that of technology. As the figures show, it is also revealed that non-oil output increases in response to technology, oil price, government spending and money supply.

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In this article, after defining a conceptional framework for defining and measuring shadow economy in Iran a close attention is also paid to a more precise definition of shadow economy itself. It is also tried to estimate it's changing process and size during 1975-2007 based on the new definition. Direct and indirect approaches are also briefly discussed to estimate the shadow economy. Then, the strengths and weaknesses of each method are pointed out. So far, almost all of the researches carried out in Iran regarding estimation of shadow economy have mainly focused on structural equation modeling approach using Lisrel. Here in this paper for the first time both structural equation modeling software programs of Amos Graphics and Lisrel are applied to estimate the shadow economy in Iran. A comparison of the process and output of both software packages is also done in this research. Finally, in addition to investigating the direct effects of the causal variables, the interactional effects of them on latent variable of the shadow economy are also analyzed.

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Shadow economy is an important part of economy in almost all countries especially the developing ones. Most of active firms in this part of economy have negative externality on the environment. Considering the importance of sustainable development and growing international pressures to maintain and support the environment more and more attentions have been drawn to the factors affecting and threatening environmental health. The present paper for the first time considers the role of variables like polity index and active population to total population ratio and how they affect the shadow economy. In addition to the main direct effects of these variables on shadow economy the indirect effects of causal variables through interaction with shadow economy are also examined. Since the relationship between shadow economy and air pollution has been somehow disregarded in economic literature to a large extent in Iran and to some extent at international level the present paper for the first time focuses on the relationship between shadow economy and air pollution. The results indicate that on average the ratio of shadow economy to GDP is 12.25% and a 1% increase in the size of the shadow economy raises the water pollution by 0.17%.