France has been among the first countries to become secularized but has preserved a Catholic identity. Before 2008, French laws made it very difficult to collect data on an individual’s religious affiliation. The dataset "Enquête Mode de Vie des Français" is the first allowing one to collect such data.
Researcher Thomas Baudin used this data to investigate in the impact that being a Catholic has on fertility in France. He tried to find answers on two main questions: 1. Do Catholic people have more children than others? 2. Why is this the case?
Baudin shows that practicing Catholics have more children than the rest of the population, while this is not verified for nominal Catholics. He also constructed two variables allowing him to detect that particularized ideology mechanisms can explain in part why religion has an impact on fertility in his dataset. Nevertheless, he couldn't exclude the social interaction hypothesis. A multivariate analysis validates the main mechanisms of the rational actor model.