Determine the Optimum and Sustainable Size of City in a Local Economy Model (the Case of Iranian Metropolises)

Today, urbanization is growing in all countries. Increasing urban population growth has led to the development in various fields especially the economy. For example, according to the World Bank's World Development Report 2019, about 16% of world GDP is produced in the 30 cities in the world. But cities development has had many problems such as pollution, noise, traffic, etc. Accordingly many residents of metropolitans see the population growth at the root of their problems And city managers are faced with the question whether there is an optimal size for the city and if there is, what is its limits? In this paper, the optimal and sustainable size of the metropolises of the country has been estimated. Investigated metropolises due to lack of data, only include the cities of Tehran, Isfahan, Mashhad, Shiraz, in the year 1387 to the year 1391. The method is based on an economic model that has three local economic factors: firms, households and local government. The results showed that the size of Tehran metropolitan has crossed its sustainable and optimal size And metropolises of Isfahan, Mashhad and Shiraz has passed of optimal size but have a distance to the sustainable size.