Analysis of Change Trends of Small Town's Status in the Urban System of Iran from 1956 to 2006 Using Balance Sheet Model*

Population size, physical boundary and definition of political division of cities and towns of an urban system change over time period. These changes can be led to the functional changes of them. Change of small town’s population is an important factor in urbanization process and urban system. Thus, the purpose of this research is to evaluate the change trends of small town’s (25 to 100 thousand people) status in the urban system of Iran in recent 50 years and wants to answer to this question that “which factors have influenced on changes of number and population of small towns?” The prevailing approach to this research is descriptive – analytical in which balancesheet model has been used to analyze changes in the number and population of small towns and the factors influencing these changes over the period of recent 50 years from 1956 to 2006. In balance sheet model, changes of number and population of a certain class of cities is the result of six factors including the growth of cities from lower classes / to upper classes, decline of cities from upper class / to lower classes, creation of new towns and loss of towns? According to the results gained by balance sheet model, small towns in all decades have grown in terms of number and population. In the all decades, population growth of towns in lower class into small town’s class, and growth of small towns into upper class are the most important factor influencing on changes of the number and population of small towns. In terms of “by place” changes, population growth of small towns increased from 49 percent in period 1956-1966 to more than 80 percent, and decreased to 27 percent in period 1996-2006. In terms of “by class” changes, growth of these towns increased from 54 percent in 1956-1966 to more than more than 77 percent in 1976-1986 period, and decreased to 12 percent in period of 1996-2006. Also in terms of “by class” changes, in-class changes and growth of cities are the most important factors of growth of these towns. in decades 1986 -1996 and 1996 – 2006 were created considerable number of new small towns, especially in the periphery of national metropolitan (Tehran), that in most cases lack real functions of small towns and rather act as habitants for over population of Tehran metropolitan. Thus, in two recent decades (1986-2006), creation of new small towns, especially in Tehran province, is one of influencing parameters on small town’s population growth.