Peer effects and the onset of childbearing in an urban context in Latin America

Public policy
Education - Health
Poverty - Inequality - Aid Effectiveness

The influence of peers is a determinant of fertility related decisions. In communities where adolescent pregnancy is salient (unimportant) individuals tend to accelerate (delay) the onset of their childbearing.

Peer Effects and the Onset of Childbearing in an Urban Context in Latin America

In the last decades there has been a substantial reduction in total fertility in Latin American and the Caribbean (LAC) region. On average, the reduction in fertility rates for women ages 25-44 (adult population) has been faster than the reduction of the fertility rate for teenagers (Florez and Soto, 2007). As a result, adolescent fertility has become a more important component of total fertility in most of the LAC countries. Using the information of fertility rates compiled by the World Bank1, one can observe that in 1999 adolescent fertility was 15.72% of total fertility in developing LAC countries, and by 2010 this ratio increased to 16.29%.

An earlier onset of childbearing in the LAC region could have negative implications in terms of economic and human development. Pregnancy at early age, especially adolescent fertility, has been widely associated with negative socio-economic outcomes for the mother and the child. Several studies in the literature on adolescent fertility remark the fact that educational achievements, health markers, and measures of involvement in risky behaviors tend to be worse for adolescent mothers and their children. The reader may want to look for these references in Morales (2013), the extended version of this article2.

In my paper Peers Effects on a Fertility Decision: an Application for Medellín Colombia, I specified an equation to explain the chosen timing for the onset of childbearing in an urban context in Colombia. In the paper, I emphasize the role that peer effects may play in this decision. The hypothesis of peer effects has been widely studied in social sciences. Broadly speaking, this is the phenomenon that takes place when an individual behavior is partly explained by the influence of other individuals’ behavior. There are several channels through which these effects may take place; for example, individuals may learn from peer’s behavior (social learning), or they may embrace the norms of the community in regards to socially accepted practices (social influence) (Kohler, Behrman and Watkins, 2001).

After applying frontier methodological strategies to achieve identification of the endogenous peer effects coefficient, I found evidence of existence of these social interactions, which are statistically and economically significant. The peer group of reference in this research is a group of neighbors with similar socioeconomic characteristics. The estimated models reveal that a reduction on the average age at first childbirth of the peer group will cause a significant time reduction in the individual’s onset of childbearing. In other words, in terms of the fertility decision analyzed in the paper, women seem to behave in similar ways to their peer group. The magnitude of the endogenous peer effect coefficient, which is the measure of influence of the peer group, may vary depending upon the definition of the reference group, but in all cases this influence is positive and significant. This result is also robust to the selection of the sample. In addition, the estimations show that higher educational achievements before pregnancy, especially completing high school and college (complete or incomplete), have positive and significant effects. This means that more educated women decide to delay childbearing in comparison with women with lower educational achievements. One important consideration about these results is that I am able to control for reverse causality issues derived from the simultaneity of educational and fertility decisions. Given that I observe women at several times in their lives, I am able to specify the equations in terms of the characteristics of a mother before the childbirth.

The results of the best specification presented in the paper show that an increase of one year in the peers group’s average age at first childbirth implies an increment of the mother age at first childbirth of 0.7 years. In the case of education, women with college or some college delay on average almost 3 years the onset of their childbearing in comparison to women with incomplete elementary or not education at all. The delay for women with complete high school in comparison to the ones with incomplete elementary is, on average, one year and half. Using the estimated models the paper presents a computation of a measure of the individual’s respond to an increase of 10 percentage points in the prevalence of adolescent pregnancy among her reference group. If the prevalence of adolescent pregnancy increases by 10 percentage points, this will cause a half year reduction on individual’s onset of childbirth.

These results constitute evidence that peer effects may be one of the explanations for the reduction on the average onset of childbearing observed in several LAC countries in last decades. An important concern to point out is that socioeconomic segregation is a factor that exacerbates potential negative consequences of peer effects. In segregated cities, individuals in poor neighbors have as peers women that have had their onset of childbearing earlier than the population average. In a situation like this, peer effects can be seen as a factor contributing to the formation of poverty traps. Any social policy that contributes to a more random spatial distribution of households in the city would help to reduce the negative consequences of social interactions in fertility decisions. Peer effects may have desirable consequences as well, for instance, they may magnify good spillover effects of education. This may have important consequences in the reduction of adolescent pregnancy. As it was remarked earlier, education has the ability to delay the onset of childbearing. Therefore, increments in the share of peers with college, for example, will have an additional effect in delaying the onset of childbearing through social interactions. An increment of 25 percentage points in the share of peers with college or some college will cause a delay of approximate half year in the onset of childbearing through social interaction only, in addition to the direct effect that education has on delaying the onset of childbearing.

1. The source of this computations is the World Bank Development Indicators, WDI, available in

2. Available in the series of Borradores de Economia, Banco de la República.



Flórez, Carmen and Soto, Eugenia (2007). "Fecundidad adolescente y pobreza Diagnóstico y lineamientos de política" Departamento Nacional de Planeación (Colombia), 2007

Kohler, Hans-Peter, Behrman, Jere R. and Watkins Susan C. (2001) "The Density of Social Networks and Fertility Decisions: Evidence from South Nyanza District, Kenya" Demography, Vol. 38, No. 1 (Feb., 2001), pp. 43-58

Morales, Leonardo (2013). "Peers Effects on a Fertility Decision: an Application for Medellín Colombia," Borradores de Economía 777, Banco de la República de Colombia.


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