One of the factors that change the results of the expansionary monetary policy through the credit channel on the economy is the financial frictions that affected Iran's economy especially in the 2002’s and 2022’s. These frictions are manifested in variables such as capital adequacy violations, the ratio of nonperforming loans, the ratio of fixed assets to the total assets of banks, and the government's net debt to banks. In this article, with the help of building a macro structural econometric model in the period of 1968-2022, the effect of expansionary monetary policy on the change of each type of financial friction has been investigated and compared with emphasis on the endogeneity of money on Iran's economy. The obtained results show that due to the endogeneity of money, the influence of the central bank's monetary policy on the real sector of the economy has decreased and most of its effect is manifested in nominal variables such as liquidity, inflation rate and exchange rate. In addition, an increase of one standard deviation in the ratio of nonperforming loans reduces the impact of the expansionary monetary policy on the real sector of the economy more than other mentioned financial frictions. After that, the decrease in capital adequacy, the increase in the government's net debt to banks, and the increase in the ratio of fixed assets to total assets are in the next level of importance of reducing the effectiveness of monetary policy.1.IntroductionIran’s economy heavily relies on banks to finance economic entities, emphasizing the crucial impact of monetary policy through the credit channel. However, the effectiveness of monetary policy on the real sector of economy can be impeded by financial frictions. These frictions intervene in financial transactions and may increase the costs associated with obtaining external financing, such as loans, for investors (Farzinvash et al., 2014). Empirical evidence suggests that, despite high liquidity, Iran’s economy has encountered a credit crunch, especially during the period spanning from 2002 to 2022. This credit crunch can be attributed to violations of prudential ratios, including capital adequacy, nonperforming loan ratio, fixed asset ratios to total bank assets, and the government’s net debt to banks.As a consequence of these frictions, banks face resource shortages and resort to borrowing from the Central Bank through overdrafts. This results in an expansion of the monetary base, subsequently increasing liquidity and leading to a rise in the general price level. Consequently, owing to the endogeneity of money in Iran’s economy, the Central Bank lacks an independent monetary policy instrument to effectively achieve its goals. The impact of liquidity on the real sector of economy is limited, with most impact observed in nominal variables and manifested as price increases.In this respect, the present study aims to examine the impact of financial frictions on the effectiveness of expansionary monetary policy through the credit channel, specifically focusing on the endogeneity of money. Additionally, it tries to compare the respective effects of the frictions on the Iranian economy. The analytical perspective ensures the distinctive and innovative aspect of the study.2.Materials and MethodsConcerning the period from 1968 to 2022, a large-scale macroeconometric model was developed based on aggregate supply–aggregate demand frameworks and national income accounting. The research model encompasses various components, including consumption and investment expenditures, government activities, foreign trade, production, money and credit, general price levels, exchange rates, and the balance of payments. Data for constructing the model was sourced from the Central Bank’s Time Series Data Bank, the Central Bank’s balance sheet, (non-)governmental banks balance sheets, the Statistical Centre of Iran, and the World Bank.The model consisted of 28 behavioral equations, 9 connecting equations, and 91 identities. Auto-Regressive Distributed Lag (ARDL) method was used to estimate the model equations, and all equations were concurrently solved through dynamic simulation. The study relied on the criteria such as Root Mean Square Percentage Error (RMSPE) and the Theil index of inequality (U) to test the model’s performance.3.Results and DiscussionIn order to investigate the influence of individual financial frictions on the impact of expansionary monetary policy on Iran’s economy, the study assumed an annual one standard deviation increase in bank debt to the central bank as a monetary policy instrument in each considered scenario. The scenario development period spans five years, from 2018 to 2022, where the baseline trend represents the state of implementing solely expansionary monetary policy while keeping all types of financial frictions invariable in the current state of Iran’s economy.Moreover, in case of one standard deviation alteration in each financial friction during the implementation of expansionary monetary policy, it can be used to classify capital adequacy, nonperforming loans ratio, the government’s net debt to banks, and fixed asset ratios to total bank assets in the scenarios 1, 2, 3, and 4, respectively (see Table 1). Table 1. The average percentage deviation of the simulated values of the important endogenous variables in the examined scenarios from the base simulated values during the period 2018–2022Scenario 4:Increase in the fixed asset ratios to total bank assetsScenario 3:Increase in the government’s net debt to banksScenario 2:Increase in the nonperforming loan ratio Scenario 1:Reduction in capital adequacy of banksVariables-18.63-23.33-24.9-22.13Depth of bank credits-3.16-3.25-3.22-2.86Production capacity utilization rate-5.14-6.14-6.38-5.96Investment-1.82-2.3-2.4-2.24Employment-1.94-2.26-2.36-2.39Total factor productivity-2.84-3.2-3.3-3.23Gross domestic product-3.1-3.49-3.6-3.52Non-oil gross domestic product12.8913.8413.8414.19Changes in inventories19.3731.4235.4236.24Liquidity3.15.185.935.81Inflation rate7.3312.4414.1114.36Exchange rate* Source: Research resultsTable 1 illustrates that the impact of expansionary monetary policy varies across different scenarios examined. Scenario 2 (i.e., the increased ratio of nonperforming loans) impacts both the real and nominal sectors of economy by causing more significant fluctuations in these variables compared to the baseline simulation. Scenarios 1, 3, and 4 hold subsequent degrees of importance in diminishing the effectiveness of monetary policy.4.ConclusionBased on the findings, it can be concluded that the effectiveness of expansionary monetary policy on the real economy weakens the most when the nonperforming loan ratio increases, compared to three other financial friction indicators. Therefore, to mitigate nonperforming loans in banks, the study suggests that economic policymakers focus on controlling inflation rates, exchange rates, fluctuations in gross domestic product, and fluctuations in investment in the real estate sector. The priority should also be given to monitoring the decline in the quality of bank management due to the increase in the ratio of bank credit balance to total volume deposits after deducting the legal reserves. It is also worth noting that the proper implementation of Islamic contracts by banks can significantly contribute to reducing nonperforming loans.