نشریه مدلسازی اقتصاد سنجی
سال هشتم شماره 1 (پیاپی 29، بهار 1402)

The Covid-19 crisis was first recognized as a serious threat to public health around the world, but as it grew into a pandemic all over the globe, it inflicted enormous losses on the economies of many countries grappling with tackling its grip. The negative effect of this crisis has been different between countries and the role of governments turned to be a decisive one in dealing with it; The aim of this research has been to investigate the effect of the covid-19 shock on the public sectors of 19 developed and 24 developing countries for the period ranging from 2020 to 2022 using a panel vector autoregressive (PVAR) model run on seasonal data. The results show that the covid-19 crisis has led to an all the way down to an increase in healthcare expenditures, budget deficits, government size and a slump in tax revenues. What makes the patterns witnessed in these two groups of countries different is the degree of the effect the crisis had on aforementioned variables. The results show that overall, the developing countries have been affected the most by the crisis.

The main goal of this research is to examine and test the asymmetric effects of monetary policy on the production of Services. For this purpose, hidden cointegration analysis and Autoregressive distributed lag (ARDL) approach in Iran's economy have been used in the period from 1353 to1399.Hodrick Prescott filter was used to extract the positive and negative impulses of the liquidity variable. Then, the effects of positive and negative impulses of the variables were investigated separately on the positive and negative impulses of the production of this sector with latent cointegration analysis. In the last step, the long-term relationship between the variables is checked and the long-term coefficients are calculated using the auto-regression model approach with non-linear distribution intervals and the bounds test. The results showed that there is a hidden co-accumulation between the time series of M2 and production in the industrial sector.The results showed that there is a hidden cointegration between the time series of M2 and production in the Services sector. So that the positive components of the M2 and production in this sector have a long-term relationship with each other, as well as their negative components. Also, the effect of the positive shocks of M2 is greater than the negative shocks of this variable. Therefore, the existence of asymmetry in monetary policy was confirmed.

Investigating the effect of oil price uncertainty on the consumer price index of countries dependent on oil revenues is of great importance. Oil revenues in oil exporting countries are among the most important and influential factors in macroeconomic variables. As the risk increases due to oil price uncertainty, the government budget is affected and this leads to the consumer price index being affected. The present study examines the effect of oil price uncertainty on the consumer price index using the quantile regression econometric model based on wavelet transformation during the period from April 2011 to April 2021 in Iran. The results of the empirical model estimation showed that the relationship between oil price uncertainty and consumer price index is inverse. In other words, with the increase of uncertainty in the price of oil, the consumer price index will decrease, and this effect is greater in the final digits than in the initial digits. Also, according to the estimation results of the wavelet transformation model, the negative effect of oil price uncertainty on the consumer price index is greater in the long term than in the short term.

One of the new ideas to reduce inequality and adjust the class gap is the "sharing economy" model. By creating "access instead of ownership", the sharing economy has provided the conditions for the low income deciles to use some life facilities in which there is a large class gap, and a part of the lack of consumption in the low deciles (caused by the lack of ownership) decreases.In this research, while introducing the "sharing economy" model in order to improve the inequality situation in the country, focusing on the issue of "trust" as the most important challenge of this economic model, an effort is made to design a mechanism to increase the level of trust in the sharing economy. , to provide the basis for inclusive and sustainable growth of this economic model in the country. For this purpose, by using the game theory and one of its sub-branches called mechanism design theory, a trust-building mechanism with the aim of increasing the level of trust in online accommodation sharing platforms. , the design and then the proposed mechanism is evaluated. The results of the evaluation show that the proposed mechanism in this research is "compatible with motivation", "individually rational", "efficient" and "has a balanced budget predicted in advance".

One of the signs of a healthy economy is the stability of macroeconomic components such as exchange rate, inflation, budget deficit, and foreign trade sector. In the current study, using the TVP-QVAR model, in the period of 1385:01-1397:12, with a monthly frequency, the method of transfer, receive, and also the cause of transfer of volatilities between exchange rate, inflation, budget deficit, and the current account has been investigated. The research results showed that if the growth of the variables is at low, average, and high levels, the type of communication between them will also be different. Specifically, there has been more relationship between research variables' volatilities in low and high growth rates. Also, in the case of a high growth rate, only the exchange rate volatilities cause inflation, current account deficit, and government budget deficit. On the other hand, the government budget deficit has affected the current account deficit only in the case of a low growth rate.

The government's debt to commercial banks can have an effect on the monetary base and liquidity through the effect on the balance sheet of commercial banks and through the balance sheet of the central bank. In Iran's economy, despite the growth of 32.6 and 19.9 percent of public sector debt to commercial banks in 2017 and 2018, which was accompanied by 22.1 and 23.1 percent growth of liquidity, it is formed by examining the components of this hypothesis that the components Government debt to commercial banks can affect liquidity and its components. The data used in this study include the monetary base, liquidity, money, quasi-money, economic growth rate, inflation rate, government debt to commercial banks and government companies and institutions debt to commercial banks, which are from the official statistics of the Central Bank of Iran for the period They were taken in 1998-2020. In this research, it has been tried to investigate and evaluate the effects of government debt to commercial banks on the components of Iran's liquidity by using the method of non-linear regression model with distribution breaks (NARDL). The results show that the shocks of the government's debt to commercial banks in the long and short term have a symmetrical effect on the basis of money, money, liquidity and quasi-money; In addition, the shocks of the government and government institutions' debt to commercial banks also have an asymmetric effect on the dependent variables.