The aim of this study is to determine how physical expansion and urban redevelopment affect the population distribution and population mobility in the metropolitan area of Istanbul. In the study, the spatial change of the population at the district and neighbourhood level in the 2013-2017 period was examined. In the first stage, the population change, macro-form developments, housing production in the 2000-2017 period were examined and the magnitude of the spatial change was revealed. And in the second stage, the spatial distribution of population mobility in the city was examined. The study covers 39 districts in the metropolitan area of Istanbul. In order to determine the urban change, the built environment in the metropolitan area of 2000, 2007, 2012, and 2017 were compared and for this purpose, the CORINE database, Google, and Yandex maps were used. The population data of the same period were obtained from the general population census and address-based population registration system database fin - the neighbourhood and district levels. Population mobility between districts was obtained from the TurkStat intro- and inter-provincial migration database. In addition, one of the most important indicators explaining population mobility and spatial concentration in the metropolitan area is building occupancy permits on a district basis, and these data were obtained from the TURKSTAT Construction Statistics database. Some of the variables were obtained from previous studies on Istanbul. "Stratified regression analysis" was used in the study. When the net migration data of the districts of Istanbul received from both other provinces and other districts of Istanbul are evaluated; districts that receive immigration from both other provinces and other districts of Istanbul (Region-I) are Esenyurt, Sancaktepe, Arnavutkoy, Tuzla, Cekmekoy, Beylikduzu, Buyukcekmece, Silivri, Sile, Catalca, Maltepe, and Basaksehir districts. The districts that give population to other provinces but receive immigration from other districts of Istanbul (Region-II) are Eyupsultan, Kartal, and Pendik districts. Avcilar, Bagcilar, Bahcelievler, Bakirkoy, Bayrampw, Beykoz, Beyoglu, Esenler, Fatth, Gaziosman-pasa, Gungoren, Kadikoy, Kagithane, Kucukcekmece, Sultangazi, Umraniye and Zeytinburnu (Region-III) are the districts that give population to other provinces and Istanbul's other districts. Finally, districts that receive immigration from other provinces but immigrate to other districts of Istanbul (Region-IV) are Sisli, Besiktas, Uskudar, Sariyer, Atasehir and Sultanbeyli districts. In the 2013-2017 period, 1.4 million people moved out to other addresses within Istanbul. The population movement is bidirectional, from centre to periphery and vice versa. Another dimension of the population mobility in Istanbul is the locational preferences of foreign nationals. According to the study conducted by the International Organization for Migration (IOM) in Istanbul in 2018, 60% of the foreign nationals (refugees and migrants) in Istanbul live in the 3rd region. In other words, foreign nationals take the place of the locals, moving out of core areas to the fringes. The cost of rent, security concerns, transport systems, urban redevelopment, inclination to work in places with irregular economic activities, and desire to live close to the established migrant population arc all elements that contribute to this preference. According to the results of the regression analysis, only the new housing permits determine the inward migration (R-2 =0.892). Outward migration is determined by the population of the district, quality of life and population density (R-2 =0.875). Physical thresholds in the metropolitan area of Istanbul prevent urban sprawl and this causes an intense urban development demand. This dense metropolitan development pattern is shaped by limitations such as inadequate public resource allocation for strong public transport infrastructure, and limited or high-cost land to develop new cities, topography, sea, or protected areas. It is observed that the urban area expands more slowly compared to the population growth, so the gross density has also increased. When the population change at the neighbourhood level after 2013 is examined, a significant decrease in the population in the central regions of the metropolitan area and significant population increases along the corridors in the periphery were detected. It has been determined that there is deconcentration and expansion in the metropolitan area, but there is very little change in the form of suburbanisation, decentralisation, sprawl and rural dispersal. Population mobility in a metropolitan area at this scale causes difficulties in estimating population distribution in urban planning. The estimation of the spatial distribution of the population is vital in transport planning, provision of public services, and infrastructure planning. The results obtained in this study can be used in long-term estimates of the spatial distribution of the population.
