Spatial structure of city population growth

Sandro M. Reia (1) , P. Suresh C. Rao (1) , Marc Barthelemy (2) , Satish V. Ukkusuri (1)

1 Purdue University [West Lafayette]
2 IPHT - Institut de Physique Théorique - UMR CNRS 3681

We show here that population growth, resolved at the county level, is spatially heterogeneous both among and within the U.S. metropolitan statistical areas. Our analysis of data for over 3,100 U.S. counties reveals that annual population flows, resulting from domestic migration during the 2015-2019 period, are much larger than natural demographic growth, and are primarily responsible for this heterogeneous growth. More precisely, we show that intra-city flows are generally along a negative population density gradient, while inter-city flows are concentrated in high-density core areas. Intra-city flows are anisotropic and generally directed towards external counties of cities, driving asymmetrical urban sprawl. Such domestic migration dynamics are also responsible for tempering local population shocks by redistributing inflows within a given city. This "spill-over" effect leads to a smoother population dynamics at the county level, in contrast to that observed at the city level. Understanding the spatial structure of domestic migration flows is a key ingredient for analyzing their drivers and consequences, thus representing a crucial knowledge for urban policy makers and planners.

Keywords: Metropolitan Statistical Areas; Internal Migration; Urbanization; Relocation Flows; City Growth

Domains: Physics [physics]

Sandro M. Reia, P. Suresh C. Rao, Marc Barthelemy, Satish V. Ukkusuri. Spatial structure of city population growth. Nature Communications, 2022, 13, pp.5931. ⟨10.1038/s41467-022-33527-y⟩. ⟨cea-03772912v2⟩