Determine of Sustainable City Size and Compare with Actual Size Case Study: Metropolises of Iran

The purpose of this study is to determine the sustainable size of the metropolises of Iran during the years 2006-2015, by using the surplus function, based on the presence of the government as a provider of public goods and services. For this purpose using the total surplus function approach which is defined by the difference between the total income and the total expenditure of the households working and living in the large cities, the sustainable size of the metropolises of Iran is estimated. Findings of this research show that the total benefits and total costs increase as population of cites increases.The comparison of sustainable and actual values of Iranian metropolises shows that the sustainable city size of Tehran and Mashhad is less than the actual population they have and only 83% of the total population of Tehran and 91% of the total population of Mashhad can gain net benefits. But for other metropolises of Iran, the sustainable city size is more than the actual population From among the metropolises of Iran, Urmia has the highest and Esfahan has the least incentive to migrate