Fertility rates in nearly all countries will be too low to sustain population levels by the end of the century, and most of the world's live births will be occurring in poorer countries, according to a global study.
This, said researchers, will lead to a “baby boom” and “baby bust” divide across the world, with the boom concentrated in low-income countries that are more susceptible to economic and political instability, said senior researcher Stein Emil Vollset from the Institute for Health Metrics and Evaluation (IHME) at the University of Washington.
The study, reported in The Lancet, projects 155 of 204 countries and territories worldwide, or 76%, will have fertility rates below population replacement levels by 2050. By 2100, that is expected to rise to 198, or 97%, researchers estimated.
The forecasts are based on surveys, censuses and other sources of data collected between 1950 and 2021 as part of the Global Burden of Diseases, Injuries and Risk Factors Study, reports Reuters.
More than three-quarters of live births will occur in low- and lower-middle-income countries by the end of the century, with more than half in sub-Saharan Africa, researchers said.
The global fertility rate – the average number of births per woman – has fallen from around five children in 1950 to 2.2 in 2021, data show.
By 2021, 110 countries and territories (54%) had rates below the population replacement level of 2.1 children per woman.
The study highlights a particularly worrying trend for countries like South Korea and Serbia, where the fertility rate is less than 1.1 child per female, exposing them to challenges of a dwindling workforce.
Many of the most resource-limited countries "will be grappling with how to support the youngest, fastest-growing population on the planet in some of the most politically and economically unstable, heat-stressed and health system-strained places on earth”, said Vollset.
While tumbling fertility rates in high-income countries reflect more opportunities for education and employment for women, researchers said the trend signals an urgent need for improvement in access to modern contraception and female education in other regions.
In addition, “once nearly every country’s population is shrinking, reliance on open immigration will become necessary to sustain economic growth”, said the IHME’s Natalia Bhattacharjee, a co-author of the report.
The authors noted that predictions were limited by quantity and quality of past data, especially for the 2020 to 2021 Covid-19 pandemic period.
Already in China, meanwhile, a number of hospitals have halted baby delivery services as industry experts warn of an “obstetric winter”, due to declining demand amid a record drop in new births.
In the past two months, various hospitals have announced the suspension of these services.
The closures come as Chinese policymakers grapple with how to boost young couples’ desire to have children as authorities face a growing demographic headache of a rapidly ageing society.
The country’s population fell for a second consecutive year in 2023 as the record-low birth rate and high deaths due to Covid-19 accelerated a downturn officials fear will have profound long-term effects on the economy’s growth potential.
The most recent available data from the National Health Commission showed the number of maternity hospitals dropped to 793 in 2021 from 807 in 2020.
Many women opt to remain childless due to high childcare costs, and an unwillingness to marry or put their careers on hold, in a traditional society where they are still seen as the main caregivers and where gender discrimination remains rife.
Authorities have tried to roll out incentives and measures to boost the birth rate, including expanding maternity leave, financial and tax benefits for having children and housing subsidies.
Study details
Global fertility in 204 countries and territories, 1950–2021, with forecasts to 2100: a comprehensive demographic analysis for the Global Burden of Disease Study 2021
GBD 2021 Fertility and Forecasting Collaborators
Published in The Lancet on 20 March 2024
Summary
Background
Accurate assessments of current and future fertility—including overall trends and changing population age structures across countries and regions—are essential to help plan for the profound social, economic, environmental, and geopolitical challenges that these changes will bring. Estimates and projections of fertility are necessary to inform policies involving resource and health-care needs, labour supply, education, gender equality, and family planning and support. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 produced up-to-date and comprehensive demographic assessments of key fertility indicators at global, regional, and national levels from 1950 to 2021 and forecast fertility metrics to 2100 based on a reference scenario and key policy-dependent alternative scenarios.
Methods
To estimate fertility indicators from 1950 to 2021, mixed-effects regression models and spatiotemporal Gaussian process regression were used to synthesise data from 8709 country-years of vital and sample registrations, 1455 surveys and censuses, and 150 other sources, and to generate age-specific fertility rates (ASFRs) for 5-year age groups from age 10 years to 54 years. ASFRs were summed across age groups to produce estimates of total fertility rate (TFR). Livebirths were calculated by multiplying ASFR and age-specific female population, then summing across ages 10–54 years. To forecast future fertility up to 2100, our Institute for Health Metrics and Evaluation (IHME) forecasting model was based on projections of completed cohort fertility at age 50 years (CCF50; the average number of children born over time to females from a specified birth cohort), which yields more stable and accurate measures of fertility than directly modelling TFR. CCF50 was modelled using an ensemble approach in which three sub-models (with two, three, and four covariates variously consisting of female educational attainment, contraceptive met need, population density in habitable areas, and under-5 mortality) were given equal weights, and analyses were conducted utilising the MR-BRT (meta-regression—Bayesian, regularised, trimmed) tool. To capture time-series trends in CCF50 not explained by these covariates, we used a first-order autoregressive model on the residual term. CCF50 as a proportion of each 5-year ASFR was predicted using a linear mixed-effects model with fixed-effects covariates (female educational attainment and contraceptive met need) and random intercepts for geographical regions. Projected TFRs were then computed for each calendar year as the sum of single-year ASFRs across age groups. The reference forecast is our estimate of the most likely fertility future given the model, past fertility, forecasts of covariates, and historical relationships between covariates and fertility. We additionally produced forecasts for multiple alternative scenarios in each location: the UN Sustainable Development Goal (SDG) for education is achieved by 2030; the contraceptive met need SDG is achieved by 2030; pro-natal policies are enacted to create supportive environments for those who give birth; and the previous three scenarios combined. Uncertainty from past data inputs and model estimation was propagated throughout analyses by taking 1000 draws for past and present fertility estimates and 500 draws for future forecasts from the estimated distribution for each metric, with 95% uncertainty intervals (UIs) given as the 2·5 and 97·5 percentiles of the draws. To evaluate the forecasting performance of our model and others, we computed skill values—a metric assessing gain in forecasting accuracy—by comparing predicted versus observed ASFRs from the past 15 years (2007–21). A positive skill metric indicates that the model being evaluated performs better than the baseline model (here, a simplified model holding 2007 values constant in the future), and a negative metric indicates that the evaluated model performs worse than baseline.
Findings
During the period from 1950 to 2021, global TFR more than halved, from 4·84 (95% UI 4·63–5·06) to 2·23 (2·09–2·38). Global annual livebirths peaked in 2016 at 142 million (95% UI 137–147), declining to 129 million (121–138) in 2021. Fertility rates declined in all countries and territories since 1950, with TFR remaining above 2·1—canonically considered replacement-level fertility—in 94 (46·1%) countries and territories in 2021. This included 44 of 46 countries in sub-Saharan Africa, which was the super-region with the largest share of livebirths in 2021 (29·2% [28·7–29·6]). 47 countries and territories in which lowest estimated fertility between 1950 and 2021 was below replacement experienced one or more subsequent years with higher fertility; only three of these locations rebounded above replacement levels. Future fertility rates were projected to continue to decline worldwide, reaching a global TFR of 1·83 (1·59–2·08) in 2050 and 1·59 (1·25–1·96) in 2100 under the reference scenario. The number of countries and territories with fertility rates remaining above replacement was forecast to be 49 (24·0%) in 2050 and only six (2·9%) in 2100, with three of these six countries included in the 2021 World Bank-defined low-income group, all located in the GBD super-region of sub-Saharan Africa. The proportion of livebirths occurring in sub-Saharan Africa was forecast to increase to more than half of the world's livebirths in 2100, to 41·3% (39·6–43·1) in 2050 and 54·3% (47·1–59·5) in 2100. The share of livebirths was projected to decline between 2021 and 2100 in most of the six other super-regions—decreasing, for example, in south Asia from 24·8% (23·7–25·8) in 2021 to 16·7% (14·3–19·1) in 2050 and 7·1% (4·4–10·1) in 2100—but was forecast to increase modestly in the north Africa and Middle East and high-income super-regions. Forecast estimates for the alternative combined scenario suggest that meeting SDG targets for education and contraceptive met need, as well as implementing pro-natal policies, would result in global TFRs of 1·65 (1·40–1·92) in 2050 and 1·62 (1·35–1·95) in 2100. The forecasting skill metric values for the IHME model were positive across all age groups, indicating that the model is better than the constant prediction.
Interpretation
Fertility is declining globally, with rates in more than half of all countries and territories in 2021 below replacement level. Trends since 2000 show considerable heterogeneity in the steepness of declines, and only a small number of countries experienced even a slight fertility rebound after their lowest observed rate, with none reaching replacement level. Additionally, the distribution of livebirths across the globe is shifting, with a greater proportion occurring in the lowest-income countries. Future fertility rates will continue to decline worldwide and will remain low even under successful implementation of pro-natal policies. These changes will have far-reaching economic and societal consequences due to ageing populations and declining workforces in higher-income countries, combined with an increasing share of livebirths among the already poorest regions of the world.
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