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Harmonizing Historical Trade Using Geopolitical Data: A Multilayer Network Approach to Bilateral Flows, 1830–1938

Paul Girard will be the guest at this seminar session. He will present, with Béatrice Dedinger and Guillaume Daudin, their paper on the reconstruction of international trade networks between 1830 and 1938, based on various historical data. He will discuss the methods used to standardize these data in order to analyze the dynamics of trade globalization and imperial expansion.

Event, Research Seminar

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Salle K.008, 1 Place St-Thomas d'Aquin, 75007 Paris

Abstract

This paper presents a methodological framework for reconstructing historical bilateral trade networks spanning 1830-1938, using trade data from the RICardo database — a collection of over 570,000 bilateral trade flows reported by national customs administrations. The core challenge lies in the extreme heterogeneity of the 2,350 trading entities in the dataset, which include not only countries and colonies but also cities, groups of countries, and geographical areas. Roughly 22% of all bilateral flows involve at least one such "miscellaneous" entity, making quantitative analysis difficult.

To address this, the authors build yearly multilayer networks by combining trade flows with geopolitical relationship data from their GeoPolHist dataset. They develop a three-pronged transformation strategy — aggregation, ratio-based splitting using adjacent-year networks, and gravity-model imputation — to convert complex entity pairings into standardized bilateral flows between countries or colonies. Their method resolves approximately 75% of the flows involving miscellaneous entities (accounting for 19.4% of total trade value), yielding a 156% average increase in trade network density (from 1.6% to 4.3%). While the approach does not eliminate all heterogeneity — some large areas remain unresolvable and missing source data persists — the reconstructed networks offer a valuable new tool for studying the drivers and consequences of 19th- and 20th-century trade globalization, including the economic motivations behind imperial expansion such as the Scramble for Africa.

Biographies

Paul Girard is co-manager of OuestWare, a Nantes-based agency specializing in data analysis and visualization solutions. His core expertise lies in designing and developing human-data interfaces that combine software engineering, interface and information design, and data science. His career includes ten years as technical director of the Sciences Po médialab, where he led multidisciplinary projects bringing together engineers, social science researchers, and designers. Today, he works on both academic digital humanities projects and commercial data analytics solutions, while also consulting on data strategy and interaction design.

Béatrice Dedinger is an Associate Researcher at the Centre d'histoire de Sciences Po, where she specializes in the economic history of international trade and its statistical dimensions from the early nineteenth century to the present. Trained as an economic historian, she is particularly recognized for her expertise in the history of German commerce and the development of historical trade statistics for geopolitical entities worldwide. Her current research includes the digitization and quantitative analysis of international trade data, notably within the framework of the RICardo project, thereby combining economic history and digital methods.

Guillaume Daudin has been Professor of Economics at the University of Paris-Dauphine (LEDa-DIAL) since 2012. From 2016 to 2019 he was President of the French Society for Economic History. His areas of expertise include the economic history of the early modern period and the globalization of trade. His most recent research focuses on 18th-century French trade (see http://toflit18.medialab.sciences-po.fr), the long Anglo-French trade war of the 18th century, the profits from the slave trade, contemporary value-added trade, and the significance of additional costs in international trade since 1974. He has contributed to a number of public-facing research websites (eg http://toflit18.medialab.sciences-po.fr/#/home and https://anr.portic.fr/acces-data-sprint/). For full CV, see https://gdaudin.github.io/.

Practical informations

Date: September 22nd, 2026

Time: 2:00 PM - 3:30 PM

Location: room K.008, 1 Place Saint-Thomas d'Aquin, 75007 Paris

Language: English

Registration is mandatory via this link.