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Today the role of tax system is based on three primary political, social and economic goals. its biggest task is to defend economic security of economic agents as well as being known as an income method Economic insecurity has led to the increase in size of the underground economy, so itreduces amounts of investments in the economy .This phenomenon has a negative effect on the tax base and reduces tax revenues. The main objective of this paper is to investigate the relationship between tax revenue and economic security in Iran during the period of 1977-2011. For this purpose, we used the Hsiao's- Granger and Toda & Yamamoto (TY) causality tests. The results show that there is a unilateral causality from the economic to security tax revenue. The economic Health and security of the country is subject to the healthy tax structure. Through establishing Strong tax system, creating appropriate cultural and encouraging people to pay taxes, economic structure of the country will be stronger. So according to the ratio of tax revenues to GDP is low and there is bilateral causal relationship between this variable and economic security, the tax system requires a fundamental review to provide financial security and investment. Consequently, tax revenues increase.

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Wagner law is the first model of government expenditures in the public finance literature. In addition to testing the traditional version of Wagner's law, also the augmented version of this law, which is introduced by Murthy (1994) is examined in order to find a long-term relationship between government spending and economic development in Iran. The main objective of this study is to evaluate a short-term and long-term relationship between government expenditures (per capita) and GDP (per capita) using annual data for the Iranian economy during the period 1392-1357. Therefore, in this article, the validity of this relationship is checked by six different formulations of the Wagner Law (the desire to increase government spending by economic growth), and the causality between variables are considered with using boundary F-test and error correction model (ECM). Among the studied models, the Wagner law is executable in terms of income elasticity only in Peacock and Musgrave version and in generalized version. The results of the Bound Test indicate that long-term relationship between the variables exists in three versions of Wagner’s law. In addition, causality test with using an error correction model represents a one-way path from the income on government spending for short periods in five models. Overall, the results show that the Wagner law is confirmed in the third group of models for short-run in the Iranian economy.

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According to the Kau and Rubin (K&R) hypothesis, increasing the government's power to collect taxes, through increased tax revenues, expand the public sector expenditure. In this regard, the main objective of this paper is to empirically test the relationship between government's power to collect taxes, tax revenues and government expenditures in Iran during the period of 1971-2013. For this purpose, rate of female participation in the labor market and self-employment rate is used as two variables which are the indicators of government's power to collect taxes, and Toda and Yamamoto granger causality method is used. The Results show no causality relationship from the government's power to collect taxes indicators toward government spending (Rejection of the Kau and Rubin hypothesis). The reason for this conclusion is justified based on the absence of causality relationship from government's power to collect taxes indicators toward tax revenue; however, the causality relationship from tax revenues toward government expenditure is approved (confirm of the Friedman's hypothesis). According to other results, the causal relationship from the oil revenues toward government expenditure and tax revenues is confirmed.
 

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The purpose of this Research is to investigate the causal relationship between the stock price index in the insurance industry, banking sector, and the investment sector during 2009 – 2017 period. So, a long-term relationship between variables was investigated by Johansson-Juselius test. Then, by Vector error correction model (VECM), the causal relation between the variables of the model was studied. According to the results, the existence of long-term Granger causality is confirmed from stock prices in banking sector and investment sector indices toward insurance industry. Also, the existence of a long-term Granger causality from insurance industry and banking sector toward investment sector is not confirmed, but there is a long-term causal relationship from Insurance industry and investment sectors toward banking sector. Only a short-run causal relationship is found from stock price index of insurance industry and stock price index of banking sector toward investment sector. Banking sector has a negative impact on insurance industry, which indicates the Substitution effect of banking sector in insurance industry. It can also be argued that if the stock market is a good indicator of economic environment, the insurance sector and banking sector act ineffectively in persuading investment, which indicates a necessity for revision on the subject.
 

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Real exchange rate misalignment means that the real exchange rate deviates from its equilibrium level and is the cause of many domestic and global economic problems. This index is considered as an important indicator in foreign competition and in case of adopting an inappropriate exchange rate regime; it may create economic instability and affect economic performance. This issue is important in countries with oil resources due to the special structure of their foreign trade. Therefore, the purpose of this study is to investigate the short-term and long-term causal relationships between the exchange rate regime and the real exchange rate misalignment in the OPEC countries. Therefore, using panel data during the years 2020-2000 and cointegration approaches, long-term and short-term causal relationships between these variables have been investigated. The results show that in the short run, the causal positive and significant relationship has been obtained from the real exchange rate misalignment to the exchange rate regime; In other words, higher the real exchange rate misalignment, the more the monetary authority intervenes in the market to move the exchange rate towards greater stability and minimize fluctuations. In the long run, the causal relationship between the exchange rate regime and the real exchange rate misalignment is negative and significant. This means that as the exchange rate regime moves towards more stability, the real exchange rate misalignment decreases. In other words, the type of exchange rate regime in the long run can lead to the formation of market expectations and, consequently, increase or decrease imbalances.

 

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Dollarization is one of the issues that occurs to maintain the purchasing power of economic units in a country during sudden exchange rate shocks, and it can affect all markets, especially the stock market. The purpose of this article is to use the Lag-Augmented Vector Autoregressive (LA-VAR) model to evaluate the dynamics of Granger causality relationships between the exchange rate, partial dollarization and stock market in Iran's economy. For this aim, monthly data was used for the period from March 2009 to November 2022. The findings of the Recursive Evolution (RE), Revolving Window (RO) and Forward Expansion (FE) algorithms showed that there was no causal relationship between the exchange rate and the stock market return. Only in the period of April 2017 to November 2019, there has been the bidirectional causality between the exchange rate and stock market return, and after that, the causality direction has been from the exchange rate to stock market return. Also, the exchange rate and dollarization causality results indicated that the exchange rate was the Granger causality of dollarization from January 2012 until November 2013, after which the exchange rate has increased from 18000 IRR to 30000 IRR and the index of dollarization increased from 0.3 to 0.5. On the other hand, in most of the period from 2018 to the fall of 2020, the exchange rate has been the dollarization Granger causality. So, according to the shocks source, an appropriate policy should be considered for the exchange rate or the dollarization possibility.