Global age-sex-specific fertility, mortality, healthy life expectancy (HALE), and population estimates in 204 countries and territories, 1950-2019: a comprehensive demographic analysis for the Global Burden of Disease Study 2019

Abstract

Background: Accurate and up-to-date assessment of demographic metrics is crucial for understanding a wide range of social, economic, and public health issues that affect populations worldwide. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 produced updated and comprehensive demographic assessments of the key indicators of fertility, mortality, migration, and population for 204 countries and territories and selected subnational locations from 1950 to 2019.

Methods: 8078 country-years of vital registration and sample registration data, 938 surveys, 349 censuses, and 238 other sources were identified and used to estimate age-specific fertility. Spatiotemporal Gaussian process regression (ST-GPR) was used to generate age-specific fertility rates for 5-year age groups between ages 15 and 49 years. With extensions to age groups 10-14 and 50-54 years, the total fertility rate (TFR) was then aggregated using the estimated age-specific fertility between ages 10 and 54 years. 7417 sources were used for under-5 mortality estimation and 7355 for adult mortality. ST-GPR was used to synthesise data sources after correction for known biases. Adult mortality was measured as the probability of death between ages 15 and 60 years based on vital registration, sample registration, and sibling histories, and was also estimated using ST-GPR. HIV-free life tables were then estimated using estimates of under-5 and adult mortality rates using a relational model life table system created for GBD, which closely tracks observed age-specific mortality rates from complete vital registration when available. Independent estimates of HIV-specific mortality generated by an epidemiological analysis of HIV prevalence surveys and antenatal clinic serosurveillance and other sources were incorporated into the estimates in countries with large epidemics. Annual and single-year age estimates of net migration and population for each country and territory were generated using a Bayesian hierarchical cohort component model that analysed estimated age-specific fertility and mortality rates along with 1250 censuses and 747 population registry years. We classified location-years into seven categories on the basis of the natural rate of increase in population (calculated by subtracting the crude death rate from the crude birth rate) and the net migration rate. We computed healthy life expectancy (HALE) using years lived with disability (YLDs) per capita, life tables, and standard demographic methods. Uncertainty was propagated throughout the demographic estimation process, including fertility, mortality, and population, with 1000 draw-level estimates produced for each metric.

Findings: The global TFR decreased from 2·72 (95% uncertainty interval [UI] 2·66-2·79) in 2000 to 2·31 (2·17-2·46) in 2019. Global annual livebirths increased from 134·5 million (131·5-137·8) in 2000 to a peak of 139·6 million (133·0-146·9) in 2016. Global livebirths then declined to 135·3 million (127·2-144·1) in 2019. Of the 204 countries and territories included in this study, in 2019, 102 had a TFR lower than 2·1, which is considered a good approximation of replacement-level fertility. All countries in sub-Saharan Africa had TFRs above replacement level in 2019 and accounted for 27·1% (95% UI 26·4-27·8) of global livebirths. Global life expectancy at birth increased from 67·2 years (95% UI 66·8-67·6) in 2000 to 73·5 years (72·8-74·3) in 2019. The total number of deaths increased from 50·7 million (49·5-51·9) in 2000 to 56·5 million (53·7-59·2) in 2019. Under-5 deaths declined from 9·6 million (9·1-10·3) in 2000 to 5·0 million (4·3-6·0) in 2019. Global population increased by 25·7%, from 6·2 billion (6·0-6·3) in 2000 to 7·7 billion (7·5-8·0) in 2019. In 2019, 34 countries had negative natural rates of increase; in 17 of these, the population declined because immigration was not sufficient to counteract the negative rate of decline. Globally, HALE increased from 58·6 years (56·1-60·8) in 2000 to 63·5 years (60·8-66·1) in 2019. HALE increased in 202 of 204 countries and territories between 2000 and 2019.

Interpretation: Over the past 20 years, fertility rates have been dropping steadily and life expectancy has been increasing, with few exceptions. Much of this change follows historical patterns linking social and economic determinants, such as those captured by the GBD Socio-demographic Index, with demographic outcomes. More recently, several countries have experienced a combination of low fertility and stagnating improvement in mortality rates, pushing more populations into the late stages of the demographic transition. Tracking demographic change and the emergence of new patterns will be essential for global health monitoring.

Funding: Bill & Melinda Gates Foundation.

Figure 1

TFR by country or territory, 2000 and 2019 Each point represents the TFR for a country or territory in 2000 and 2019. The size of the point indicates the absolute annualised rate of change in total fertility rate between 2000 and 2019. Points above the diagonal line show countries or territories that have seen an increase in TFR between 2000 and 2019, whereas those below the diagonal had a decline in TFR between 2000 and 2019. GBD=Global Burden of Diseases, Injuries, and Risk Factors Study. TFR=total fertility rate.

Figure 2

Annual change in under-5 deaths by GBD super-region, 1970–2019 The annual change in under-5 deaths is defined as the simple difference between deaths in the under-5 age group from the current year and the year before. Different colours show the annual changes in under-5 deaths from the different GBD super-regions. The height of the bar indicates the number of deaths. GBD=Global Burden of Diseases, Injuries, and Risk Factors Study.

Figure 3

Life expectancy at birth by sex and GBD super-region, 1950–2019 Each line shows life expectancy at birth globally or for a GBD super-region, indicated by colour, between 1950 and 2019. GBD=Global Burden of Diseases, Injuries, and Risk Factors Study.

Figure 4

Distribution of probability of death by age, in 1990, 2000, and 2019 The graph shows the distribution of probability of death by age group for the years 1990, 2000, and 2019, calculated for the 204 countries and territories included in this study and plotted in a natural logarithmic scale. The boxes indicate the middle 50% of the distribution (75th and 25th percentiles) and the mean (horizontal bar in the box), while the whiskers indicate the middle 95% of the distribution (97·5th and 2·5th percentiles).

Figure 5

Years lived in poor health in 1990 and 2019 The scatter plot shows years lived in poor health, calculated by subtracting HALE from life expectancy at birth, for 1990 and 2019. Datapoints are coloured by GBD super-region. GBD=Global Burden of Diseases, Injuries, and Risk Factors Study. HALE=healthy life expectancy.

Figure 6

Life expectancy at birth and fit of expected value based on SDI, 2019 The scatter plot shows estimated life expectancy at birth in years for 204 countries and territories coloured by super-region for 2019. The dashed black line represents life expectancy that is predicted on the basis of SDI, with 95% uncertainty intervals shaded. GBD=Global Burden of Diseases, Injuries, and Risk Factors Study. SDI=Socio-demographic Index.

Figure 7

Difference between observed life expectancy and expected life expectancy by decade Datapoints show the difference between observed life expectancy and the expected life expectancy at birth based on SDI by country or territory for every tenth year between 1950 and 2010, and for 2019. The black line shows the mean difference by year over time. GBD=Global Burden of Diseases, Injuries, and Risk Factors Study. SDI=Socio-demographic Index.

Figure 8

Annual change in global total population by GBD super-region, 1950–2019 The stacked bar chart shows the changes in global total population from year to year. The height of the bar (or, when there is negative change from a region, for example in the 1990s and 2000s in central Europe, eastern Europe, and central Asia, the difference between the height of the bar above zero and the height of the bar below zero) indicates the total annual change in global population. GBD=Global Burden of Diseases, Injuries, and Risk Factors Study.

Figure 9

Percentage of the population younger than 15 years of age or aged 65 years and older, in 1950 and 2019 This figure shows the long-range changes in the distribution of population at the national level from 1950 to 2019. For reference, countries with the top ten population size in 2019 are shown in green. The grey lines connect the countries and territories with the most substantial changes between the two years of comparison. Codes within the graph are ISO 3 codes. GBD=Global Burden of Diseases, Injuries, and Risk Factors Study. AND=Andorra. BGD=Bangladesh. BIH=Bosnia and Herzegovina. BRA=Brazil. CHN=China. GRL=Greenland. GUM=Guam. IDN=Indonesia. IND=India. JPN=Japan. KOR=South Korea. NGA=Nigeria. PAK=Pakistan. PRI=Puerto Rico. RUS=Russia. SGP=Singapore. THA=Thailand. TWN=Taiwan (province of China).

Figure 10

Stage of demographic transition by location, 2019 The map shows the distribution of locations across five stages of demographic transition in 2019. No countries or territories were in the before transition or early transition stages. Late demographic transition and post demographic transition locations are differentiated between those with net emigration and those with net immigration.