Global Urban Demographic Change and Migration Patterns

The demographic structure of urban populations shapes global economic development1,2, political stability3,4, and the impact of climate hazards 5,6. Cities of different sizes with youthful or aging populations, as well as changes in migration patterns can have different economic trajectories7 as labor markets expand or contract and can determine which demographic groups are most vulnerable to extreme heat8, flooding9 and air pollution10. Similarly, large young male populations have the potential to cause political instability4. As such, understanding the patterns and changes in these demographic structures for each city globally is paramount for determining sustainable development and growth strategies across different cities5. However, we currently lack a globally comprehensive, city-level assessment of how and where urban demographic patterns are evolving. Here we measure the spatiotemporal variability in demographic structures and migration patterns for 13,135 cities worldwide between 2000 and 2020. We find that changes in the demographic structure are highly heterogeneous across the urban continuum, with higher dependency ratios in small and medium cities compared to large cities. We highlight key cities with rapidly changing, unbalanced demographic structures that deviate from official, coarse-grained statistics. Further, we show that in-migration accounts for 52% of the 782 million new urban residents added to all cities between 2000 and 2020. The heterogeneous urban demographic patterns that we uncover are key for designing locally appropriate policies to actualize policies for sustainable urban economic development, climate change adaptations, and political stability, especially for smaller cities within low- and middle-income countries.