Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2025 Sep 16;122(37):e2501504122.
doi: 10.1073/pnas.2501504122. Epub 2025 Sep 12.

The coherence of US cities

Simone Daniotti  1   2   3 , Matté Hartog  4 , Frank Neffke  1
Affiliations

The coherence of US cities

Simone Daniotti et al. Proc Natl Acad Sci U S A. .

Abstract

Diversified economies are critical for cities to sustain their growth and development, but they are also costly because diversification often requires expanding a city's capability base. We analyze how cities manage this trade-off by measuring the coherence of the economic activities they support, defined as the technological distance between randomly sampled productive units in a city. We use this framework to study how the US urban system developed over almost two centuries, from 1850 to today. To do so, we rely on historical census data, covering over 600M individual records to describe the economic activities of cities between 1850 and 1940, as well as 8 million patent records and detailed occupational and industrial profiles of cities for more recent decades. Despite massive shifts in the economic geography of the United States over this 170-y period, average coherence in its urban system remains unchanged. Moreover, across different time periods, datasets, and relatedness measures, coherence falls with city size at the exact same rate, pointing to constraints to diversification that are governed by a city's size in universal ways.

Keywords: cities; coherence; diversification; economic complexity; urban systems.

PubMed Disclaimer

Conflict of interest statement

Competing interests statement:The authors declare no competing interest.

References

    1. Youn H., et al. , Scaling and universality in urban economic diversification. J. R. Soc. Interface 13, 20150937 (2016). - PMC - PubMed
    1. Chong S. K., et al. , Economic outcomes predicted by diversity in cities. EPJ Data Sci. 9, 17 (2020).
    1. Mazzarisi O., de Azevedo-Lopes A., Arenzon J. J., Corberi F., Maximal diversity and Zipf’s law. Phys. Rev. Lett. 127, 128301 (2021). - PubMed
    1. Rosenthal S. S., Strange W. C., “Chapter 49 - evidence on the nature and sources of agglomeration economies” in Handbook of Regional and Urban Economics, Cities and Geography, Henderson J. V., Thisse J. F., Eds. (Elsevier, 2004), vol. 4, pp. 2119–2171.
    1. Hidalgo C. A., Klinger B., Barabási A. L., Hausmann R., The product space conditions the development of nations. Science 317, 482–487 (2007). - PubMed

Publication types

LinkOut - more resources