agent based modeling

Through investigating the phenomenon of tax evasion, tax experts are facing the constant challenge of designing and implementing policies to reduce tax evasion due to its hidden nature part. Agent-based models are one of the powerful tools for the behavioral simulation of tax evasion. By creating a virtual laboratory environment with agent-based models, researchers can examine the impact of different policies on people's behavior. In this research, people's behavior is modeled based on their risk-taking degree using a factor-based model; In such a way that the degree of risk-taking in this field is affected by three components of the social factors, the audit-penalty system and the amount of benefit from the public goods they received. The results emphasize the importance of paying attention to social factors, political factors, and government efficiency to reduce tax evasion behavior and increase the total amount of tax payment. The simulation result indicates that among the two audit-penalty policy combinations, a high audit and low penalty is a more suitable policy than a low audit and high penalty, and it causes the number of tax evaders to decrease, as well as the total amount of tax payment increase. Another result is that the government should pay more attention to distribution efficiency to reduce tax evasion behavior and allocation efficiency to increase total tax payments.

Nowadays, due to the globalization of the economy, the problems related to the economic situation in the countries have been given more attention. These issues and dilemmas have resulted in many consequences for societies, therefore economic inequality has become an important issue for countries and they are looking for ways to reduce it (Tanjitpiyanond et al., 2022; Vyas et al., 2022). The issues and problems that economic inequality creates for countries can sometimes lead to irreparable crises for countries (Beesley & Hawkins, 2022; Neapolitan, 1999; Stiglitz, 2012; Wilkinson & Pickett, 2010). Economic inequality is a phenomenon that classical economics hardly can clarify its exact roots and consequences, and this is because the approach of classical economics does not consider all economic aspects and cause and effect relationships between variables (Markey- Towler & Foster, 2013). Charities and non-governmental organizations are among the institutions that there is a lot of discussion about their impact in reducing economic inequality and in general the impact of charities on macroeconomics and economic inequality. Therefore, in recent years, much research has been conducted on the effect of charities and non-governmental organizations in reducing economic inequality (Arulampalam et al., 2015; Fateh Ahmad & Majid, 2022; Jaffer, 2020; Mastromatteo & Russo, 2017). At present, the activities of charities in our country are such that they do not bring about big events in solving social issues, and the main reason for the weakness of charities in making a proper impact to improve society is the existence of many trustees without a proper road map (Lotfi, 2018).

The main purpose of the current study is to investigate the effect of charities and also "the proper distribution of charities' resources" on economic inequality. Therefore, in a laboratory environment, the mechanism of "proper distribution of charity resources" is examined by designing scenarios. Because the implementation of these scenarios in real space requires high cost and time, in the present study, the agent-based modeling approach was used (An et al., 2021).One of the simulation approaches that has recently received a lot of attention in the field of social and economic sciences, especially in systems that have a lot of complexity, is agent-based modeling. In this approach, different components of a system are modeled using the concept of an agent, and in social sciences, each agent can represent a person in society, and in this type of modeling, it is also possible to define exchanges and processes between system components (Wilensky & Rand, 2015). In the present study, the simulation is implemented in the NetLogo software, and Epstein and Axtell's "Sugarscape" model was used to model the economic system of the present study (Epstein & Axtell, 1996). This model is also available in the NetLogo software standard library (Wilensky & Rand, 2015). The "Sugarscape" model has been developed based on the topic that is the main goal of the present study so that the role of charities and the way of distribution of charities' resources can be modeled and the questions raised can be examined using predetermined scenarios. Economic inequality in different scenarios is reported using the Gini coefficient index (Deltas, 2003).

Table 1 shows the results of 10 times of the implementation of different scenarios designed in this article, which briefly shows the effect of the existence of charities and also the creation of a suitable mechanism for distributing the resources of charities in the economic model studied in this article. Table 1. Statistical report of the number of people of different economic classes after 1 year By comparing the average Gini coefficient in three different scenarios, it is clear that the best economic situation in terms of economic inequality was the third scenario. The average Gini coefficient in 10 simulations of the third scenario, i.e. the second behavioral model of charities, was 0.241 and compared to the previous two scenarios, it has the lowest value. This issue can answer the second question of the present study and how to improve the performance of charities in the economic system is determined by creating a centralized database for charities. Therefore, if a centralized database is created for charities to operate in, it can increase the effectiveness of charities in improving economic conditions in the long run. It is suggested that to reduce the economic inequality in the long term, the environment of charities should be improved and to reduce parallelism and errors in identifying the real needy, a mechanism should be provided for the proper distribution of charity resources.

In the presented model, other economic factors such as producers, banks, etc. have been omitted, and only the exchange of the agents' wealth with the environment and each other has been modeled. Therefore, it will be possible that researchers to develop a model in the field of socio-economic and charitable systems. In this study, the Epstein and Excels model was developed for the effect of charities. To develop the model, another type of agent was added, in addition to the main agents of the model. The charity agent has been added as an institution to create economic balance in the model. On the other hand, the behavioral model of people has also been developed and good behavior has been modeled for them. It is in this way that it is possible to create a flow of resource distribution from the well-off people to the less well-off people of society. Two questions were asked about these issues. The first question was whether the creation of charitable institutions and good behavior by people has any effect on economic inequality. The second question is the role of the existence of a suitable distribution system of good resources in the model. For this reason, two different types of charity behavior models were developed. In the first model, charities help the agents who have referred to them, without having a database to identify the need and also to meet the needs of the people. The weakness of this model can be examined from several different aspects, which were mentioned in different parts of the model presentation. For this reason, there is a need for a system in which charities can provide their services and at the macro level of society, good resources can be distributed appropriately and purposefully among the less fortunate.

The tragedy of commons is always an inevitable phenomenon in common-pool resources exposed to residents' selfish perceptions. Many researchers of empirical studies believe that self-governing institutions that emerge within a society can solve the tragedy of the commons, but what still needs to be added in guiding this choice is a clearer picture of the mechanisms behind the institutional emergence in the successful management of common-pool resources. Agent-based models provide a suitable tool for this task due to their extraordinary capacity to connect micro and macro levels. This The presents study seeks to develop a simple abstract model of the institutional emergence pattern by introducing the possibility of cheat and enforcement, which has been observed in renewable common-pool resource issues. This article study uses the ADICO institutional grammar as a basic structure to model the institutional rules and define the users' strategies. Users modify their behavior through a transformational process and establish a management institution to manage common-pool resources, eventually leading to many advantages for users and common-pool resources. The results show that even within this simplified model, the self-governing institutions maintain the resource balance at a stable level and improve the average income of the users compared to the open access in all social networks.

The distribution of income and wealth in Iran is highly dependent on monetary policy. Iran's macroeconomic variables show that the country is experiencing an increase in inflation, liquidity and social inequality. Given that the facility repayment rate plays a role in channeling resources to investments, and given the role of the central bank in determining and regulating this variable in Iran, this study examines the impact of changing the facility repayment rate as a monetary policy tool on macroeconomics variables related to the distribution of income and wealth in society. The contribution of this research is to provide the agent-based model for Iran and to study the effects of different scenarios of decreasing, increasing and constant trend of facility repayment rate on the distribution of income and wealth, and other macroeconomic variables.

Two types of approaches can be used to model this problem: (1) simulation with the Dynamic Stochastic General Equilibrium (DSGE) approach and (2) simulation with the Agent-based Computational Economics (ACE) approach. DSGE models seek to find the optimal point, in which pricing is done through aggregating supply and demand by the Walrasian auctioneer, and none of the factors can decide on their variables. While in ACE simulations, changing process of variables and factors is examined and each factor has the ability to decide about its variables based on its observation of the system. The ACE approach has been used because of the proximity of the simulation to reality and the ability to examine the process. In this simulation, the effect of changing the facility repayment rate on the distribution of income and wealth and other macroeconomic variables is examined in three scenarios: decreasing, increasing and fixed facility repayment rate. Agents that are considered in the proposed simulation are: (1) The Central bank as policy-maker agent that decides about facility repayment rate and money supply volume, (2) The bank is responsible for allocating credit to firms and depositing from households and distributing income from banking activities among depositors. It is also the responsibility of the bank to sell consumer goods and capital of bankrupt companies that have not been able to repay their facilities, (3) Firms are responsible for the production of consumer goods and capital and its sale in the market, and (4) A household that provides its labor force to firms in exchange for wages and provides consumer goods for its livelihood in the consumer goods market. In this simulation, policy-making is done by the central bank and the existence of the government, and fiscal policies are ignored and only the mentioned monetary policy (facility repayment rate) is investigated.In this research, the market is defined in a way that each agent on the demand side observes a random list in terms of number of factors on the supply side and buys from the supplier agent that offers the lowest price. Model have 4 markets as follows:(1) the labor market, (2) consumer goods market, (3) capital goods market, and (4) credit market. The characteristic of this type of market is that the market mechanism is a random adaptation mechanism, and all agents on the demand side have incomplete information from suppliers and vice versa. None of agents see all the market prices and decide to buy only on the basis of incomplete observations of the system. Also, on the supplier side, the firm does not see the cumulative need of the market. It means that the firm estimates the amount of production for this period based solely on its own personal experience in the previous periods, and according to that estimate, it employs labor and produces goods and services. And firms set prices based on their experience on previous periods. This kind of market attitude in simulation has caused the simulated market to be closer to the real world.

The result of this simulation shows that the repayment rate of incremental scenario caused the collapse of the simulation system and also the Gini coefficient increased, which indicates the disparity in the distribution of income and wealth in society. The fixed scenario does not show an effect on improving the Gini coefficient and on the other hand causes the bankruptcy of many firms in the long run. The best result is the reducing scenario. In this scenario, the system achieved sustainable economic growth, controlled liquidity, and a reduction in the Gini coefficient.

In the absence of speculative markets, all the money generated in the banking system is directed to the production and development of economic activities. In addition, decreasing repayment rate of facilities can improve the distribution of income and wealth in society.

In this paper, using an agent-based model, the behavior of commercial banks and investment funds is simulated. We have tried to show systemic risk transmission mechanism from the money market to the capital market through balance sheet changes. In this model, the money and capital markets are endogenously modeled and the price is determined by interest rate and stock market index in these markets respectively. 81 percent of Iranian commercial banks have a mixed portfolio of interbank loans and securities and can spread the crisis throughout the financial system in case of a shock. This process happens through the fire sale mechanism and investment fund unit redemption and can make stocks undervalued in the capital market. Although higher imposed capital adequacy and liquid assets rate can reduce the shock effect on price in the capital market, these high rates make banks portfolios mixed and increases systemic risk. Optimal capital adequacy rate is estimated 19 percent.

Households move in cities for better housing and access to better public goods services, but the public goods are not equally important for households and their spatial distribution is not uniform in the city. In order to investigate in detail, we divvied the public goods into two groups: net and gross and modeling the housing residential choice. The main purpose of the study is to measure the impact of this product among all households and high-income groups. Data were collected from Census (2016) and the neighborhood quality survey (2015-2016) of Tehran Municipality. We use agent-based model for investigate the behavior of households. The results showed that the gross public goods are effective in choosing the house of all households in the city. Among the variables in this group, for all households in the city, “access to the public transportation system” has the greatest impact, but this variable does not affect the choice of high-income households. The variable “access to educational space” also has the least impact among all households, but in the high-income group, this variable has the most impact. In the group of net public goods, all variables are effective in choosing the house of all households in the city, and the variable “security” has the greatest impact. Compared to the high-income group, except for “distance to educational space”, other variables do not have a significant effect on housing choice, which indicates the unbalanced spatial distribution of net public goods in the city and the homogeneity of spatial distribution in high-income households. Also, based on the research background, educational space in the high-income group is considered as a measure of neighborhoods quality.

Drugs as a strategic and subsidized commodity and an urgent need for patients have been constantly of particular importance, specially, in the health-care system of a society. On the other hand, one of the parameters concerning the assessment of the family welfare is the amount spent for satisfaction of divergent needs. The more a family spends on essential necessities such as food, housing, clothing and higher education, the less is expected to be devoted to health care. Concerning drugs, the demand for different drugs may vary depending on the patientschr('39') attitudes, the type of illnesses and their income elasticity. The objective of the present research is to investigate the demand for orphan drugs for refractory diseases regarding various income groups in Iran applying Agent-based Models (ABMs). In this research, the behavior dynamics of the orphan drugs applicants and the diversity of their demands in miscellaneous price scenarios resulting from inflation and fluctuations in the exchange rate have been scrutinized in accordance with ABM. To this end, one thousand family applicants for orphan drugs, extracted from Iranchr('39')s statistics center, were categorized in five different income ventiles. Their reactions towards the increase of the price of the aforementioned drugs are predicted based on Net Logo simulation software. The results indicate that the average of price elasticity of demand for generic and branded drugs has been -0.39 and -0.05 percent, respectively; similarly, the demand for these two drug groups has been decreased by the same amount. In the lowest income ventile as the price of generic and branded orphan drugs deceases, for the lowest income ventile families, the allocated expenses for these drugs has been decreased by 3.3 percent and 31.85 percent, respectively. The main reason for the aforementioned problem is assigned to the low budget of the patientschr('39') family and its allocation to essential necessities of life such as food and housing. The severity of the cost reduction in branded drugs is due to the fact that it can be replaced by generic drugs.

One of the main concerns of economic scholars and thinkers is to predict the behavior of individuals in an economic system. Although economists often use complex mathematical equations for economic analysis, in recent decades due to the weakness of forecasting analyses based on equations and inability of such equations to justify empirical events, economists have used modeling and simulation methods. In other words, they are Looking for ways to justify complex phenomena in the economy as a complex system. In addition to applying complexity theory, this research attempts to introduce a research tool to scholars for the simulation of agent-based research. In this study, we will examine the efficiency of each system by developing an agent-based model based on a No-Ponzi economic system and comparing it with a Ponzi economic model. We will also examine the effects and consequences of some economic behaviors that are contrary to the ethics and teachings of Islam. Comparing the two models, the results indicate that the No-Ponzi model has a better human development index and more social welfare.

Establishing social justice and equilibrium in society is one of the most important preconditions for development. Therefore, reducing the trend of increasing inequality for policymakers in many countries is a priority. Zakat is a financial tool in the macro system of Islamic society, which plays an important role in the effective allocation of income. The purpose of this article is to describe the theory of the role of zakat as an important tool in achieving efficiency and improving human development indicators. For this purpose, the Net Logo application has been used for agent-based modeling. This paper examines the actual effects of Zakat on the distribution of wealth in Islamic economics and compares conventional and Islamic economics. The results indicate that an Islamic economic system, in general, leads to higher human development indicators than a conventional investment model system. JEL Classification: C53, P4, D630, D310, E21

In a competitive market, the daily or hourly electricity prices are set by the intersection between power plants’ offers in an auction and consumers demand. In the Iranian semi-competitive electricity market, power plants offer their production and price schedules for the next day and the Independent System Operator (ISO) chooses the winners based on total costs of different suppliers. The producers receive the payment based on their bids and the consumers pay the set prices, which are often subsidized. The power plants also receive the fuel at subsidized prices to keep the production cost and the bidding prices low. The cheap fuel provides no incentive to the power plants to conserve fuel, which causes concerns about the efficiency and the excess pollution created by thermal plants. In this paper, we develop an agent-based model to analyze the impacts of liberalizing fuel prices on power plants production and offer prices. The model includes independent agents who learn from their own and others’ actions and adapt accordingly. We use the AMES programme to simulate the model and estimate values of variable. The results show that if the fuel prices rise by a factor of 10, the electricity prices offered by the power plants will increase by a lower factor.