Estimating adolescent birthrates in Mexico: comparison of available data sources

Introduction

In Mexico, reducing unwanted adolescent fertility is national policy priority. Adolescent fertility has increased in the context of overall sharp declines in overall fertility. Accurate estimations are needed to support the implementation and evaluation of policies aimed at reducing adolescent fertility. In Mexico, numerous data sources offer information about adolescent births. However, information regarding very young adolescents is limited, and the accuracy of these varied sources remains uncertain.

Purpose

To calculate and compare live birth rates among very young adolescents (VYA) and adolescents with four different data sources (birth certificate, census, population-based survey, and vital statistics data) at the national and state level and by year (2008-2019) and compare them with official estimations from the population agency, CONAPO. 

Methods

We utilized birth certificate data to estimate age-specific fertility rates (ASFRs) for eight age groups (10-14, 15-19, 20-24, 25-29, 30-34, 35-39, 40-44 and 45-49) from 2008 to 2019. From these ASFRs, we computed the total fertility rate (TFR) for the period. We repeated the process using survey data (ENADID 2009, 2014 and 2018), Census (2010 and 2020), and the Intercensal Survey (2015), and the vital statistics (2008-2019). We visually compared the TFRs and ASFRs overtime from these four data sources with CONAPO’s projections at the national level and by state. For very young adolescents, only three data sources were available (birth certificate, census, vital statistics).    

Results

All data sources show declines in TFR and in the ASFRs across age groups during 2008-2019. In 2019, VYA group had an ASFR of 3.24 births per 1,000 girls aged 10-14 using census data, 2.85 using birth certificate data and 1.89 births per 1,000 girls aged 12-14 with vital statistics. During the same year adolescents (15-19) had 65.1 births per 1,000 women aged 15-19 according to CONAPO’s projections, 59.8 births with census data, 56.2 with birth certificate data and 54.4 births per 1,000 women 15-19 with vital statistics. In TFR discrepancies between the data sources range from 0.50 children per woman in 2008, 0.14 children per woman in 2015, to 0.30 children in 2019. The largest difference is observed between birth certificate data and CONAPO’s projections with birth certificate estimates consistently lower except in the youngest age group (10-14).  The difference was the largest in 2011, with 2.63 births per 1,000 VYA 12-14, while the smallest was in 2016 with 0.94 births per 1,000 girls 12-14.

Discussion

Our results showed that the different data sources and national projections are mostly consistent. These findings validate the use of these diverse data sources, with attention to the strengths and limitations of each. Our results also highlight the need for additional data for the VYA group in order to provide data to support policies targeting this age group.