research

Papers and research outputs. A complete list is also available on my Google Scholar profile.

2026

Large cities lose their growth advantage as countries urbanize

Andrea Musso, Diego Rybski, Dirk Helbing, and 1 more author

Proceedings of the National Academy of Sciences, 2026

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The share of the world population living in cities with more than one million people rose from 11% in 1975 to 24% in 2025 (our estimates). Will this trend towards greater concentration in large cities continue or level off? We introduce two new city population datasets that use consistent city definitions across countries and over time. The first covers the world between 1975 and 2025, using satellite imagery. The second covers the U.S. between 1850 and 2020, using census microdata. We find that urban growth follows a characteristic life cycle. In the early stages of a country’s urbanization process, large cities grow faster than smaller ones. At later stages, growth rates equalize across sizes. We use this life cycle to project future population concentration in large cities. Our projections suggest that 38% of the world population will be living in cities with more than one million people by 2100. This estimate is higher than the 33% implied by the well-known theory of proportional growth, but lower than the 42% obtained by extrapolating current trends.

2024

How networks shape diversity for better or worse

Andrea Musso, and Dirk Helbing

Royal Society Open Science, 2024

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Socio-diversity, the variety of human opinions, ideas, behaviors, and styles, has profound implications for social systems. This paper studies how fundamental characteristics of social networks can support or hinder socio-diversity using models of cultural evolution, mathematical analysis, and numerical simulations. We find that pronounced inequalities in the distribution of connections obstruct socio-diversity, while close-knit communities, scarce long-range connections, and higher tie density tend to promote it.

2023

Equidistribution of rational subspaces and their shapes

Menny Aka, Andrea Musso, and Andreas Wieser

Ergodic Theory and Dynamical Systems, 2023

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To any k-dimensional subspace of rational n-space one can naturally associate a point in a Grassmannian and two lattice shapes. Using unipotent dynamics, this paper proves simultaneous equidistribution of all of these objects under congruence conditions when (k,n) is not (2,4).