Peers and Possible Partners: Exploring the Origins of Population Long-term Equilibria

Project Information

P3OPLE

Grant agreement ID: 101039252

DOI

10.3030/101039252

EC signature date 17 February 2022

Start date 1 September 2022

End date 31 August 2027

Funded under

• European Research Council (ERC)

Total cost

€ 1 105 303,75

EU contribution

€ 1 105 303,00

Coordinated by

ECOLE POLYTECHNIQUE
France

Periodic Reporting for period 1 - P3OPLE (Peers and Possible Partners: Exploring the Origins of Population Long-term Equilibria)

Reporting period: 2022-09-01 to 2025-02-28

Summary of the context and overall objectives of the project

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.
The first objective is to study peer effects in fertility preferences and to revisit an unsettled debate: why are some communities trapped in sub-optimally high or low fertility equilibria? The project discusses how (a) information and coordination failures, (b) conformism and competition, and (c) immigration, can prevent or facilitate fertility change.
The second objective is to study general equilibrium effects on the matching market and to raise an unexplored question: can a man be involuntarily childless due to a relative scarcity of female partners on the matching market? The project quantifies the importance of (a) imbalanced sex ratios, (b) polygamy and (c) serial monogamy as drivers of reproductive inequalities.
P3OPLE crosses the boundaries of disciplines by integrating insights from demography, sociology and evolutionary biology into economic frameworks. The methodology combines economic theory and empirical analysis, including experimental, observational and structural methods, to provide quantitative evidence on novel causal links.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

(1a) Test whether information and coordination failures may prevent the decline in fertility in Africa
We implemented a Randomized Control Trial with 14,454 households in 500 villages in rural Burkina Faso to test the idea that misperceptions about attitudes and norms systematically increased desired fertility and reduced the acceptance of modern contraception. We organized village meetings to (i) reveal the distribution of others’ views on ideal family size, relevance of pro-natalist norms and contraception; and (ii) spark community discussions. Our hypothesis was that birth rates would decline in villages where people initially underestimated the acceptability of small families. We reject this hypothesis: the village meetings had no effect on fertility.
We collected data on subjective variables related to fertility behaviors, such as expectations, preferences, first- and second-order beliefs regarding community norms, at a very large scale and at 2 moments in time (14,454 couples, men and women interviewed separately, in 2018 and 2021).

(1b) Assess the importance of conformism and competition in the diffusion and persistence of small families using a partial population experiment in China.
We analyzed the impact of the “Later, Longer, Fewer” policy introduced in the 70s in China. We find that ethnic minorities decreased their fertility, although only the majority ethnic group, the Han Chinese, were subject to birth quotas. We find that the fertility response of minorities is driven by a social channel (people do not want to deviate from the average behavior) and by an economic channel (people want to keep up in terms of resources spent per child). We conclude that conformism and competition both played a role in the diffusion and persistence of small families in China.

(2a) Quantify the extent to which imbalanced sex ratios contribute to male singleness in China.
Among single men, the annual probability to marry in 2019 was twice as low as in 1999. Estimating a structural model of the marriage market, we find that the deterioration of female-to-male ratio, known as the marriage squeeze, explains 18% of this decline. The increase in in the supply of educated people explains an additional 50%, partly due to a mismatch between educated women and less-educated men. The decrease in marital surplus, i.e. value of marriage, explains the rest.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

(1a) The literature has so far documented that community dialogues can be successful in changing views about contraception. However, most studies were not randomized, they only covered small geographic areas, and while they find impacts on contraceptive use, they do not track effects on actual fertility. Our null experimental result in Burkina Faso qualifies the existing evidence by showing that, when community-level interventions are evaluated rigorously and at a large scale, they are not so promising.
(1b) The literature on family planning policies in China generally ignores spillovers. Not only do we quantify the magnitude of the spillovers but we also dig into the mechanisms and explain under which conditions they arise. Existing research on diffusion processes focuses on spontaneous fertility transitions, in which population policies have little to no role, whereas we study transitions induced by policies. Our results on the importance of competition and conformism potentially extend to countries that experienced fast fertility declines following strict family planning programs in contexts marked by strong political ideologies (e.g. South Korea, Singapore, Iran, and to a smaller extent in Indonesia and India).
(2a) Existing quantitative models used to study the marriage squeeze in China have produced mixed results about the role of sex ratio in marriage decline. Moreover, these models fail to account for changes in the value of marriage, which have been extensively documented using qualitative methods. Our methodology is the first attempt to quantify the relative importance of different factors (not only sex ratio but also changes in education and in the value of marriage) in a unified framework. We conclude that imbalanced sex ratios contribute to male celibacy to a sizeable extent, even though changes in education and in the value of marriage seem matter even more quantitatively

The innovative dataset collected in Burkina Faso will be made accessible upon publication of the experimental results to ensure that others can use the data for their own purpose. The novelty of the data already allowed us to conduct a follow-up project in which we study the historical origins of pro-natalist preferences. We find that fertility preferences and behaviors are shaped by decades of colonial forced labor migration (young men were forcibly recruited under French colonial authorities to work in neighboring colonies for one to two years between the 1910s and 1940s). In particular, the inherited pattern of low-skill circular migration for adult men reduced reliance on subsistence farming, the accompanying need for child labor, and ultimately fertility.

In order to study peer effects in fertility decisions, we developed a new methodology to estimate heterogeneous peer effects using partial population experiments. Specifically, we relaxed the homogeneity assumption in the standard linear-in-means model of peer effects by allowing individuals to respond differently to the outcomes of other group members depending on the identity of these members. The methodology should be useful to other researchers interested in estimating the effect of a policy on eligible units and the spillover effect on ineligible units.