Insights from 19th century Paris

Researchers have just published their findings on the analysis of economic activities over a century of urban growth in the city of Paris.

The study is published in Nature Cities. The authors are Julie Gravier (Center de Recherches Historiques and Center d’Analyse et de Mathématique Sociales, EHESS) and Marc Barthelemy (Institut de Physique Théorique and Center d’Analyse et de Mathématique Sociales, EHESS).

Understanding the evolution of economic activities alongside the growth of large cities is crucial but challenging, particularly for historical periods where comprehensive data is often unavailable. In this study, the authors leverage a newly released dataset, constructed from city directories, which includes extensive records of individuals, merchants, businesses, organizations, and institutions in Paris from 1829 to 1907.

This dataset contains approximately 1 million entries of economic activities, regularly updated over a span of 79 years, offering a rare historical perspective on urban growth and economic evolution. This period also encompasses significant disruptions, such as the transformative Haussmann’s works (1853–1870) and political upheavals like the Franco-Prussian War and the Commune revolution (1870–1871).

Contemporary research on the dynamics of economic activity in cities typically spans shorter timeframes—ranging from a few years to a few decades. In contrast, the analysis of Barthelemy and Gravier covers nearly a century, providing a deeper understanding of how economic activities evolved during Paris’ expansion.

The authors showed in the case of Paris during the 19th century that not all activities are equivalent and that they can be grouped in categories with different dynamics and scaling. In particular, it seems that some activities naturally accompany the growth of the city and can be considered as intrinsic to its development.

These activities essentially answer to the basic needs of the residents, and the type of scaling with population of the number of these activities depends essentially on their underlying logic: It seems intuitive that the number of food stores scales more or less linearly with population while the number of administrative or educational needs follow an optimization logic (and scale sublinearly).

All these activities constitute the core of the city, while other activities determine its specific features. These quickly developing activities usually respond to some passing fad or to a need of the specific period and the phase of the city’s development.

These findings demonstrate that economic activities scale differently with population and suggest that while some activities are fundamental to a city’s growth, others become prominent during periods of innovation or specialization.

Additionally, Paris’ evolution should be viewed within the broader context of an urban system, as the largest city in France at the time. Urban scaling laws, which help interpret the relationship between city size and economic activity, suggest that activities with scaling exponents greater than 1 represent early stages of innovation adoption, often concentrated in large cities. Conversely, activities with exponents below 1 correspond to more mature, established activities.

The typology presented in the paper likely extends to other growing cities, highlighting how different types of activities contribute uniquely to urban development, depending on the city’s phase of growth or specialization. This analysis provides new insights into the diverse roles of economic activities in shaping the evolution of large cities.