Extended Abstract
Introduction: Findings from the empirical literature on the relationship between government size and social welfare are in most cases contradictory. In some studies, such as Kormendi, and Meguire (1986), Carr (1989), Cashin (1995) the positive impact of government size on social welfare and economic growth has been shown; Ramyand (2003), Loto (2011), Bergh and Henrekson (2011) believe there is a negative relationship between these two economic variables (Shumaila and Qayyum, 2014; Forte & Magazzino, 2011; Herath, 2011).
For example, Fournier and Johansson (2016) argue that increasing government public spending enhances potential growth. Whereas, very large governments reduce the potential growth, unless the performance of the government is very effective. Johansson (2016) also points out that excessive government size leads to reduced economic growth. In contrast, increasing social welfare spending can reduce inequality as a cost of redistribution.
Some economists such as Yasin (2011), Vedder and Gallaway (1998), Hsieh and Lai (1994) considered this relationship uncertain. (Shumaila & Qayyum, 2014(
Therefore, based on the discrepancies between the researchers’ findings, the nonlinear relationship between and social welfare can be emphasized. Thus, on the one hand, for a small government, with more investment in infrastructure and upgrade technology to increase the size of government activities and diversification in production will occur as a result of economic growth and the subsequent welfare increases.
On the other hand,  in exchange for the big government, the government’s tax has resulted government additional expenditures, which has led to inadequate allocation of resources, reduced economic activity, reduced private investment, and ultimately reduced provides growth and development (Shumaila and Qayyum, 2014(.
Also, considering the U-shaped Armey curve, which shows the non-linear relationship between government growth and government size, it is possible that the relationship between government size and welfare is also non-linear.
Method: In order to study the nonlinear effects and estimate the optimal size of government expenditure by affairs and chapters with emphasis on maximizing social welfare, the threshold regression model and Simplex linear programming algorithm were used.
Based on the theoretical foundations and empirical studies presented, the following model is used to estimate the optimal amount of government spending by affairs and chapters in order to increase social welfare:
lnW=f(ln(Gp/GDP).ln((NonGp)/GDP).lnInt.lnUrbant.lnOpent.lnLiteracyt.Subsidyt )+ut   
In the above model, lnW as the dependent variables of the model represent the logarithm of social welfare and the independent variables of the model are: ln(Gp/GDP) Logarithms of the ratio of government expenditures in different affairs and chapters of the general budget to GDP, ln((Non_Gp)/GDP) Logarithm of government spending in other seasons except for the matters  and chapters investigated, lnInt; Logarithm of Consumer Price Index at Fixed Price (2016), lnUrbant; Urbanization rate logarithm, lnOpent; Logarithm of the degree of openness of the economy (ratio of total exports and imports to GDP), lnLiteracyt, literacy rate logarithm. The Subsidy variable is a virtual variable used in the model to consider the effects of targeted subsidies on welfare. The value of this variable from 2010 onwards is equal to one and in other years, it is zero. Equation above will be estimated separately for the four main affairs (according to the classification of affairs and chapters in 2015) and 21 budget chapters separately. In order to estimate the optimal share of government size with the aim of maximizing social welfare during the period 1971-2019, Eviews software has been used.
Optimal amounts of expenditures and budget seasons with the aim of increasing social welfare percentage of GDP
The Optimal
Amount        The Optimal 
Amount    
1.1    Social Welfare    0.83    Public affairs
0.9    Health    0.1    Legislation
11.7    Economic Affairs    0.1    General
0.8    Agriculture    0.23    Judiciary
0.4    water resources    0.3    Financial services
0.25    industry and Mining    0.1    Science development
3.6    Information Technology    2.7    Defense affairs
0.9    Commerce and 
Cooperation    2    Defense
0.9    Housing and Civil 
Engineering    0.7    Order and security
1    Transportation    6.47    Social affairs
0.02    Environment    4.05    Education
3.2    Energy    0.12    Physical education
21.07    Total expenditure    0.3    Culture and art


Findings: The results show that in order to achieve maximum social welfare, the share of total government expenditure in GDP should be 21.07%. Also, the share of public, defense, social and economic affairs in GDP should reach the levels of 0.83, 2.7, 6.47, and 11.07 percent, respectively. Between budget chapters, the share of the education chapter should be 4.05% of GDP. The largest share of this chapter is due to its importance and role in the development process, reducing poverty and increasing social welfare in communities.
After the education chapter in social affairs, the information technology chapter with 3.6% and the energy chapter with a share of 3.2% of GDP in economic affairs have a high priority to maximize social welfare.
Information technology in the right conditions has proven its capability in the fields of economic and social development, especially health care, health, distance education and agriculture, business (Hill, 2002; Razavi Mashouf et al., 2018). Also, allocating funds to this chapter will lead to an efficient flow of information, goods, capital, increased job opportunities, expanded markets, better access government services, reduced costs, saving time, and enabling production, diversity, and efficient distribution of agricultural products, and the possibility of providing basic health services for the poor people in different regions (Raj et al., 2006; Memarnejad & Taghavi, 2013)
The United Nations Development Program (2006) also refers to energy as one of the most powerful weapons related to human development. In this regard, Douglas and Willem (1996) and Saghis (2005) noted that the lack of energy services is directly related to the main elements of poverty such as low level of education, limited opportunities for a decent life, livelihood activities, and conflict. Edmeh et al. (2017) state that there is a direct relationship between energy consumption and human development and that access to modern energy services is essential in meeting basic social needs and fostering human development.
Discussion: The ultimate goal of any economic system is to improve the welfare of individuals in the society. In the meantime, to determine the structure of the budget to maximize social welfare is important. Therefore, in view of the results, government resources should first be directed to economic and social affairs and then by prioritizing the chapters to the education chapters for the promotion of human capital, the information technology chapter for the efficient flow of information, goods, and capital. Increasing job opportunities, diversification and efficient distribution of products, energy chapter for access to modern services, defense chapter to maintain internal and external security according to Iran’s strategic position in the region and finally social welfare should provide livelihood for the affected people and some budget should be allocated the unemployed. As a result, government resources should be directed to matters and areas that have a greater and more positive impact on increasing social welfare.
Ethical Considerations:
Authors’ contributions
All authors contributed in producing of the research.
Funding
In the present study, all expenses were borne by the authors and they did not have any sponsors.
Conflicts of interest
The authors declared no conflict of interest.
Acknowledgments:
In this article, all rights relating to references are cited and resources are carefully listed