Social and economic transformation in the user groups of German inner cities. Making the invisible visible via a location intelligence approach with mass mobile data

Nowadays, in “past"-pandemic-times, visitor frequencies in inner cities and high streets have returned to pre-pandemic levels. Nevertheless, retailers' sales have not recovered to the same extent. The aim of the paper is to clarify whether a so-called “social transformation” of the inner city is taking place and whether this is part of the reason. For this purpose, based on Mass-Mobile-Data in a comparative GIS-Multi-Layer-Approach (Mix of Methods), different analyses were conducted in the downtown areas of major German cities (i.e. Berlin, Hamburg, Köln, Frankfurt, and Leipzig) in the years 2019 (Pre-COVID) and 2022 ("Past"-pandemic). The results show: visitor frequencies have regenerated, the temporal use of high streets has changed slightly, but the catchment area has changed massively. Accordingly, both the user groups and especially the retail-relevant purchasing power have changed seriously. In the city of Frankfurt, the shift in the social milieu has led to an average reduction in retail-relevant purchasing power of more than 500 euros per person in three years. The social transformation of the inner city is thus in full motion, affecting retail business models and hence the business models of asset managers with real estate in inner cities. Consequently, the results call for a stronger focus on user groups, their demands on the inner city, and a new definition of the inner city or its purpose respectively. The results are also relevant for policymakers and urban planners, as they make hitherto unmeasurable changes transparent.