Ecole Polytechnique: ERC grant on the role of social interactions in demography

Population challenges represent a political issue all over the world. In Asia and Europe, the average number of children per woman is less than two and continues to fall, creating pressure on pension systems, among other things. In Africa, on the other hand, the observed decline in fertility is less steep than expected by the United Nations. “Why have the models failed to predict this trajectory?” asks Pauline Rossi. As an economist and associate professor at the Centre for Research in Economics and Statistics (CREST*), she has just been awarded an ERC Starting Grant for the project P3OPLE (Peers and Possible Partners: Exploring the Origins of Population Long-term Equilibria) on these issues.

In her previous work, she has recently studied the economic incentives that may lead people to have children or not. In particular, she has described the extent to which the introduction of a pension system in Namibia, in Southern Africa, has contributed to a decline in fertility. “With this new project, I intend to analyse both the role of social norms, particularly on what is a “good” family, and the role of constraints on the formation of couples, for example if there are more men than women in a generation,” explains Pauline Rossi.

Social interactions and gender imbalances

Social norms and lack of coordination between people could explain why fertility remains high while economic conditions promote its decline: people continue to have many children to imitate others even though it is not economically favourable. “Perhaps if people were told what others really think, they would find that having a smaller family is actually socially accepted. Would that make it easier to change? This is one of the hypotheses that I intend to test with this project thanks to work I have already started with three colleagues in Burkina Faso,” explains the researcher. Among the other effects that will be explored is that of the arrival of immigrant families with a high average number of children in countries where fertility is lower. For example, how does the arrival of Syrian refugees in Turkey and Germany change the fertility of Turkish and German families?

The second focus of the project explores the constraints on couple formation, in particular the issue of childless men. This phenomenon is still under-researched and may have multiple causes. In China, for example, the one-child policy and the social preference for having a boy has led to a large imbalance in the gender distribution. The practice of polygamy in some parts of Africa and serial monogamy (divorces and remarriages) in the Western world can exclude some men from marriage. “These issues can have important social consequences,” explains Pauline Rossi.

Models and data collection

This research is therefore based on both economic models, which make it possible to quantify causal links, and fieldwork to collect data. There is currently a lack of data on issues such as social norms and personal preferences regarding family and male fertility. “The reason for this is that data has mostly been collected with the aim of measuring and predicting population growth, hence the focus on the average number of children per woman. But the average does not allow us to know the full distribution, in particular how many people remain childless,” stresses Pauline Rossi. Fieldwork is also essential to avoid misinterpretation. This is why the researcher is collaborating with French and foreign researchers in order to understand the context in countries such as China and Turkey.

Thanks to this ERC funding, Pauline Rossi will have the opportunity to recruit a team to help her with this research, which she hopes will stimulate other scientific questions and contribute to public debate and decision-making.

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