P3OPLE – Peers and Possible Partners: exploring the Origins of Population Long-term Equilibria

Population dynamics are a crucial driver of the prosperity of nations. Nowadays, fertility is too high in less developed countries, impeding their escape from poverty, and too low in more developed countries, threatening their very existence. Another concern is the global rise of childlessness among men, which correlates with mental health issues and social unrest.

P3OPLE contributes to addressing these challenges by studying how social and market interactions shape the dynamics and distribution of fertility. Pauline Rossi will introduce and test the empirical relevance of two novel concepts: high / low fertility traps and involuntary male childlessness:

  1. The first concept revolves around peer effects in fertility preferences and revisits an unsettled debate: why are some communities trapped in sub-optimally high or low fertility equilibria? Prof. Rossi will discuss how information and coordination failures, conformism and competition, as well as immigration, can prevent or facilitate fertility change.
  2. The second concept deals with general equilibrium effects on the matching market and raises an unexplored question: can a man be involuntary childless due to a relative scarcity of female partners on the matching market? She will quantify the importance of unbalanced sex ratios, polygamy and serial monogamy as drivers of reproductive inequalities.

Both concepts cross the boundaries of disciplines by integrating insights from demography, sociology and evolutionary biology into economic frameworks. The methodology will combine economic theory and cutting edge empirical analysis, including experimental, observational and structural methods, to provide quantitative evidence on novel causal links.

Finally, Pauline Rossi will build databases with information on male fertility and subjective determinants of fertility never consolidated or collected at such a large scale. They will allo researchers to answer open questions and explore novel ideas inspired by hitherto undocumented patterns.

Funded by the European Union (ERC, P3OPLE, 101039252). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council Executive Agency. Neither the European Union nor the granting authority can be held responsible for them.


Pauline Rossi – Principal investigator

Pauline Rossi is an Associate Professor of Economics (with tenure) at École polytechnique-CREST, a Research Affiliate at CEPR and a Research Fellow at the Tinbergen Institute.

Previously, Pauline was an Assistant then Associate Professor at the University of Amsterfam. She visited the Economic Growth Center at Yale University in the Fall 2019. She obtained her PhD in Economics from Paris School of Economics.

Her fields of research are Applied Microeconomics, Development Economics and Family Economics.

Personal website


Manasi Chhabra – Research Assistant (2023-2024)

Manasi Chhabra holds a Masters degree in Applied Economics from Paris School of Economics with the highest honors and a specialization in Public Policy and Development. She has previously worked as a credit risk analyst for Wells Fargo and interned with the French ministry of labour.

Her research interests lie at the intersection of Health, Gender and Development Economics. She is currently working with Prof. Rossi on her projects related to fertility transition in Africa and the population structure shifts in China.


Zheng Wang – Post-doctoral researcher (2023-2024)

Zheng Wang is a post-doctoral researcher at École Polytechnique-CREST. She obtained her Ph.D. in Economics at the European University Institute in 2023. Her research interests are in the field of Applied Econometrics, with a focus on networks and peer effects. Together with Prof. Rossi and Felix Pasquier, she is working on the development of an econometric method to study the heterogeneous peer effects of fertility decisions in China.

Vrinda Sharma – Research Assistant (2022-2023)

Vrinda Sharma holds a Master’s degree in Applied Economics from Paris School of Economics, from which she graduated with the highest honors in 2022.

Previously, she has been a short-term consultant at the World Bank. As an Undergraduate student in India, she worked for the government’s think tank and did extensive field work for the national sanitation policy.

Her research interests include Natural Resource Protection and Governance as well as Gender Economics.


  • April 2024: 

29/04: Pauline Rossi presents “The Negligible Effect of Free Contraception on Fertility: Experimental Evidence from Burkina Faso” at Institut National d’Etudes Démographiques (INED)

25/04: Pauline Rossi presents “The Negligible Effect of Free Contraception on Fertility: Experimental Evidence from Burkina Faso” at Paris-Saclay Applied Economics (PSAE, INRAE-AgroParisTech)

  • February 2024: 

Vrinda Sharma publishes a new blog on Exploring a New Semi-Automatic Approach to Map Digitalization, a process she discovered while working on the ERC P3OPLE at CREST.

Yun Xiao presents “Left over or opting out? Squeeze, mismatch and surplus in Chinese marriage markets” at Renmin University

  • December 2023:

04/12: “Long-run Impacts of Forced Labor Migration on Fertility Behaviors: Evidence from Colonial West Africa” at Paris School of Economics.

12/12: “Drivers of Fertility: Experimental Evidence from Burkina Faso (joint with Pascaline Dupas, Seema Jayachandran and Adriana Lleras-Muney)” at CEPR Symposium, Sciences Po.

  • October 2023: 

18/10: “Drivers of Fertility: Experimental Evidence from Burkina Faso (joint with Pascaline Dupas, Seema Jayachandran and Adriana Lleras-Muney)” at California Center for Population Research, University of California Los Angeles

24/10: Development Economics Series, Department of Economics, University of California San Diego

  • September 2023:

Manasi Chhabra is joining the ERC research team as a research assistant.

  • June 2023:

Zheng Wang is joining the ERC research team as a post-doctoral researcher.

  • April 2023:

Visit of Yun Xiao from Gothenburg University at CREST .

Publication of Spillovers in childbearing decisions and fertility transitions: evidence from China, with Yun Xiao in Journal of the European Economic Association.

  • March 2023:

14/03: “Burkina Faso’s Fertility Puzzle: Unmet Demand for Contraception, Social Norms, or High Returns to Quantity?” at University of Fribourg – Department of Economics

09/03: “The Roles of Contraception Access, Mortality Risk and Social Norms in Fertility Choices in Burkina Faso: A Randomized Experiment.” at Cergy Paris Université – THEMA (Théorie Économique, Modélisations et Applications – UMR 8184)

  • December 2022:

Visit of Christine Valente from University of Bristol at CREST.

  • September – December 2022:

The research project “Colonial origins of fertility behaviors: evidence on the role of forced labor migration in Burkina Faso” is presented in seminars at Georgetown University, Northwestern University, Oxford University, Université Paris-Saclay, Stanford University, Tinbergen Institute, USC and at World Bank.

  • September 2022:

Vrinda Sharma joins the ERC-P3OPLE program as a research assistant. She is working with Professor Rossi on multiple projects.