When smaller families seem contagious: a spatial look at the French fertility decline using an agent-based simulation model

Tommy Murphy, Università Bocconi
Sandra Gonzalez-Bailón, University of Oxford

France was the first country in Europe to undergo a fertility decline, but at least two additional features make that experience noteworthy: how long it took and how internal heterogeneity remained. This produced a distinctive geographical pattern: two areas of low fertility spread while two ‘islands’ of high fertility shrank until they more or less disappeared in the early 1900s. We build an agent-based simulation which incorporates both historical data on population characteristics and spatial information on the geography of France. We assess how different behavioural assumptions and network topologies cause variations in diffusion patterns, using quantitative data on the Ecclesiastical Oath of 1791 to proxy for the impact the Revolution might have had. Analysis of several simulations shows that a combination of both endogenous and exogenous factors help to explain the way in which the diffusion took place and suggests some of the mechanisms through which this was materialised.