Large cities lose their growth advantage as countries urbanize

Area of Science:

• Urban Studies
• Demography
• Geospatial Analysis

Background:

• Global urban populations are increasingly concentrated in large cities.
• Estimates show the share of people in million-plus cities rising from 11% (1975) to 24% (2025).
• Understanding future urban concentration trends is crucial for planning.

Purpose of the Study:

• To analyze urban population dynamics and project future concentration in large cities.
• To introduce novel, consistent city population datasets for global and national analysis.
• To investigate the life cycle of urban growth across different country development stages.

Main Methods:

• Developed two new city population datasets using consistent definitions: one global (1975-2025) via satellite imagery, and one US-specific (1850-2020) via census microdata.
• Analyzed urban growth patterns to identify a characteristic life cycle.
• Applied the identified life cycle model to project future population concentration in large cities.

Main Results:

• Urban growth exhibits a life cycle: large cities grow faster in early urbanization stages, with rates equalizing later.
• Projections indicate 38% of the global population will reside in cities with over one million people by 2100.
• This projection is higher than proportional growth theory (33%) but lower than current trend extrapolation (42%).

Conclusions:

• Urban population concentration in large cities is a dynamic process following a predictable life cycle.
• The findings provide a more nuanced projection of future urban growth than simple extrapolation or existing theories.
• Consistent, long-term city population data are essential for accurate demographic modeling and urban planning.