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Lack of reliable statistics relating to government debts in Iran's economy, not only has it influenced on the optimal management of resources and debt, but it has been one of the most important factors affecting the lack of theoretical and experimental literature in this field in Iranian economy; Somehow that he existence of extensive international literature in world, has led to very limited studies in Iran. In this study, the time series of government debt are calculated in four ways. Furthermore, this article has two ways to calculate the optimal ratio of government debt to gross domestic product, and then estimate financial space in Iran economy. In first way, without time series of government debts and based on a simple model this proportion was estimated at 15%. Despite the advantage of this method of not using the time series of debt due to the adoption of some assumptions that are inconsistent with the conditions of the Iranian economy, we cannot accept it easily. Therefore, the second method was investigated, in which first government debt series has been set up and then, using a smooth transition regression, the government's debt ratio was extracted which was 19 percent. Estimates performed in two ways, the highest government debt ratio has been experienced and the ratio of government debt that leads to negative economic growth, show that the government has a fiscal space to 30 or 32 percent of the government debt to GDP ratio.

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The relationship between exchange rate changes and trade balance has always been one of the major issues in theoretical literature and policy circles. A new approach to theoretical literature and empirical work suggest that the interaction of these two variables depends on a number of issues, including how each country's export and import markets interact, and the degree to which exports of goods are dependent on imports. For this purpose, in the paper, the relationship between exchange rate and trade balance in the Iranian economy is examined by considering the crucial role of Intra –industry trade in the form of smooth transition regression model for the period 2001: 4 to 2018: 4. The results showed that the coefficient of effect of the exchange rate on the trade balance in each period is affected by the intra--industry index, so that the lower the index, the less the effect of the exchange rate increase on the trade balance, and as this index improves, the impact is greater. This means that the positive effects of money devaluation on the trade balance can be benefited when the competitiveness of domestic products with similar foreign goods in each sector increases.