Examining Shifts in Spatial Population Concentration Indices across Iran's First to Fifth Development Plans (1989-2015)

The objective of this research paper is to analyze the trends observed in spatial population concentration indices within the context of regional and urban balance policies during Iran's first to fifth development plans spanning the period of 1989 to 2015. The study employs a trend analysis methodology, utilizing data derived from Iran's censuses. The findings of the research reveal a consistent inclination of population movement towards urban centers, despite the articulation of regional and urban balance objectives in all development plans. This phenomenon manifests in two distinct forms of population centralization. Firstly, a persistent, overarching pattern of national-level centralization emerges as the gravitational center of population settlements in the country. Secondly, a more localized and variable form of centralization is observed in the regional context, wherein certain areas function as regional centers of population agglomeration. Over the duration of the first to fifth development plans, there is evidence of a decline in urban primacy. Interestingly, cities classified as second-tier (with populations ranging between 100,000 and 250,000) exhibit the highest rates of population growth, while cities belonging to middle-tier categories (with populations ranging between 10,000 and 99,999) experience a negative population growth. In conclusion, the overall outcomes indicate a slight amelioration in regional and urban imbalances. Consequently, a shift is observed in the spatial distribution of regional and urban populations, transitioning from an extreme periphery-center structure towards a periphery-semi-periphery arrangement.