Although our method is very simple and omits various aspects of urbanization, it nonetheless yields valuable insight into long-term SSP-specific urbanization trends to inform discussion of sustainable urban policies.Įxplosive growth in urban populations presents a wide range of societal, environmental, and economic consequences in developing nations, in particular, many aspects of urban infrastructure are inadequate already for the needs of today’s population, and accommodating rapid future growth will require major improvements in urban planning 1, for which accurate population estimates are essential. Our projection strategy advances urban-population research by producing urban-size projections-for agglomerations around the world-that correctly obey empirically observed distribution laws.

We also demonstrate that, although detailed urbanization trajectories differ for different SSP scenarios, in all cases, the largest projected agglomerations of the future are more populous than the largest agglomerations today. Our results suggest that urban growth in this century will produce increasingly concentrated cities, some growing to enormous sizes. Here, working within the Shared Socioeconomic Pathways (SSPs) and using a simple urban-growth model, we estimate population trends throughout the 21st century for ~20,000 urban agglomerations in 151 countries. Future population projections of urban agglomerations furnish essential input for development policies and sustainability strategies.

Global distribution of alpha + cities