Population and fertility by age and sex for 195 countries and territories, 1950–2017: a systematic analysis for the Global Burden of Disease Study 2017
Level 3 - non-randomized controlled study
Level 3 by design analogy (longitudinal demographic time-series modeling and cohort-component analysis across 195 countries and territories).
OpenAlex W2899825622 · doi:10.1016/s0140-6736(18)32278-5
What was done
The authors reconstructed population and fertility trends from 1950 to 2017 across 195 countries and territories by single calendar year and single year of age using the demographic balancing equation. Input data included 7,817 location-years of vital registration, 1,406 birth history surveys and censuses, 1,257 population censuses, and 761 population registry location-years. Age-specific fertility rates (ASFRs) and total fertility rates (TFRs) were modeled using spatiotemporal Gaussian process regression, with linear regression applied for sparse age brackets (10–14 and 50–54 years). Population estimates were adjusted for underenumeration and age misreporting, with migration modeled using a Bayesian framework incorporating refugee data, combined via cohort-component projections.
What was found
From 1950 to 2017, global TFR decreased by 49.4% (95% UI 46.4–52.0%), dropping from 4.7 (4.5–4.9) to 2.4 (2.2–2.5) livebirths per woman. Maternal ASFR for ages 10–19 years decreased from 37 (34–40) to 22 (19–24) per 1,000 women. Global population increased by 197.2% (193.3–200.8%), from 2.6 billion (2.5–2.6) in 1950 to 7.6 billion (7.4–7.9) in 2017, averaging an increase of 83.8 million people annually since 1985. Annual population growth peaked at 2.0% in 1964 before declining to 1.1% in 2017. The global mean age rose from 26.6 to 32.1 years, and the working-age fraction (15–64 years) rose from 59.9% to 65.3%. In 2017, TFR ranged from 1.0 (0.9–1.2) in Cyprus to 7.1 (6.8–7.4) in Niger. Between 2010 and 2017, 33 countries (mostly in Europe) experienced negative population growth, while 33 of 46 sub-Saharan African countries had annual growth exceeding 2.0%.
Why it matters
This study provides a unified, transparent demographic framework linking standardized fertility, mortality, and migration estimates across seven decades. It documents the transition toward an aging global population and shifting demographic burdens between high-income regions and sub-Saharan Africa.
Limits
Estimates for countries lacking complete vital registration depend heavily on statistical modeling and imputation. Fertility in extreme maternal age groups (10–14 and 50–54 years) relied on linear extrapolation due to data sparsity. Net migration estimates remain subject to uncertainty, particularly regarding undocumented migration and sudden refugee movements.
Cited by
- supports Society is currently experiencing a massive drop in fertility and birth rates are well below replacement level.