Economic development, urban cycles, and social dynamics: discriminating polycentric from mono-centric structures with the rank-size rule

The present study reconnects the hegemonic concept of polycentric development with an operational approach investigating metropolitan hierarchies with the rank-size rule, assuming City Life Cycle theory as the reference framework. Likely for the first time in the literature, we applied the Zipf's law to the urban–rural gradient of built-up land parcel’s areas within a European metropolitan region (Athens, Greece) along a building cycle from urbanization to re-urbanization (1948–2018). The fit of Zipf’s law to real data was verified using a linear regression model that incorporates relevant predictors of land parcel’s size. We assumed a slope coefficient for parcel’s rank close to one as an indicator of mono-centrism; a slope lower than one delineates a relaxation of the settlement hierarchy possibly reflective of polycentric development. The rank-size rule applied to land parcel’s size was verified separately for all observation years, resulting more significant in remote times (1948 and 1975) and less significant in recent times (1990, 2000, 2006, 2012, 2018). Slope coefficients were found systematically lower than 1, declining slightly over time. These results suggest a latent shift from a traditionally mono-centric structure (1948) to moderately polycentric settlements (2018). We identified fractal dimension and the distance from neighboring built-up parcels and the main urban nodes, as the predictors most significantly associated with land parcel’s size. Contributing to the classification of mono-centric and polycentric models, our approach identifies—through simplified analytical tools—the main economic and non-economic factors shaping long-term expansion of contemporary cities in Europe.