Patrick Gerland

United Nations Organization · Department of Economic and Social Affairs (DESA)

This technical paper proposes a methodology for inferring the age and sex profiles of net migration. This approach enhances the capability of the Population Division of the United Nations Department of Economic and Social Affairs (United Nations Population Division) to estimate and project populations for the World Population Prospects (WPP). The a...

As part of its work in revising population estimates and projections for the biennial publication of the World Population Prospects (WPP), the United Nations Population Division produces age-specific fertility estimates for all countries and areas of the world, starting from 1950 up to today. These estimates are based on data from several reference...

Report available: https://www.un.org/development/desa/pd/sites/www.un.org.development.desa.pd/files/undesa_pd_2022_tp-methodprotocol.pdf As part of its work in revising population estimates and projections for the biennial publication the World Population Prospects (WPP), the Population Division of the United Nations Department of Economic and Soci...

Background Understanding the age pattern of under-5 mortality is essential for identifying the most vulnerable ages and underlying causes of death, and for assessing why the decline in child mortality is slower in some countries and subnational areas than others. The aim of this study is to detect age patterns of under-5 mortality that are specific...

Available online: https://www.un.org/development/desa/pd/sites/www.un.org.development.desa.pd/files/wpp2022_summary_of_results.pdf The 2022 Revision of World Population Prospects is the twenty-seventh edition of official United Nations population estimates and projections that have been prepared by the Population Division of the Department of Econ...

Background The Sustainable Development Goals (SDGs), set in 2015 by the UN General Assembly, call for all countries to reach an under-5 mortality rate (U5MR) of at least as low as 25 deaths per 1000 livebirths and a neonatal mortality rate (NMR) of at least as low as 12 deaths per 1000 livebirths by 2030. We estimated levels and trends in under-5 m...

The sex ratio at birth (SRB) is defined as the ratio of male to female live births. The SRB imbalance in parts of the world over the past several decades is a direct consequence of sex-selective abortion, driven by the coexistence of son preference, readily available technology of prenatal sex determination and fertility decline. Estimation and pro...

Introduction Skewed levels of the sex ratio at birth (SRB) due to sex-selective abortions have been observed in several countries since the 1970s. They will lead to long-term sex imbalances in more than one-third of the world’s population with yet unknown social and economic impacts on affected countries. Understanding the potential evolution of se...

Data supplement 2 for: Chao F, Gerland P, Cook AR, Guilmoto CZ, Alkema L, Projecting sex imbalances at birth at global, regional and national levels from 2021 to 2100: scenario-based Bayesian probabilistic projections of the sex ratio at birth and missing female births based on 3.26 billion birth records. BMJ Global Health 2021;6:e005516.

Data supplement 3 for: Chao F, Gerland P, Cook AR, Guilmoto CZ, Alkema L, Projecting sex imbalances at birth at global, regional and national levels from 2021 to 2100: scenario-based Bayesian probabilistic projections of the sex ratio at birth and missing female births based on 3.26 billion birth records. BMJ Global Health 2021;6:e005516.

Background: The global health community is devoting considerable attention to adolescents and young people, but risk of death in this population is poorly measured. We aimed to reconstruct global, regional, and national mortality trends for youths aged 15-24 years between 1990 and 2019. Methods: In this systematic analysis, we used all publicly...

Introduction: Skewed levels of the sex ratio at birth (SRB) due to sex-selective abortions have been observed in several countries since the 1970s. They will lead to long-term sex imbalances in more than a third of the world’s population with yet unknown social and economic impacts on affected countries. Understanding the potential evolution of sex...

Information about how the risk of death varies with age within the 0-5 age range represents critical evidence for guiding health policy. This paper proposes a new model for summarizing regularities about how under-5 mortality is distributed by detailed age. The model is based on a newly compiled database that contains under-5 mortality information...

The sex ratio at birth (SRB) is defined as the ratio of male to female live births. The SRB imbalance in parts of the world over the past several decades is a direct consequence of sex-selective abortion, driven by the co-existence of son preference, readily available technology of prenatal sex determination, and fertility decline. Estimation and p...

In low income and lower-middle income countries, data from civil registration systems do not allow monitoring excess mortality during the COVID-19 pandemic. Rapid mobile phone surveys aimed at measuring mortality trends on a monthly basis are a realistic and safe option for filling that data gap. The data generated by mobile phone surveys can play...

This report provides a detailed overview of the methodology used to produce the 2019 revision of the official United Nations population estimates and projections, prepared by the Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat. The 2019 revision is the twenty-sixth round of global population es...

Available at: https://population.un.org/wpp/Publications/Files/WPP2019_Highlights.pdf The 2019 revision of the World Population Prospects is the twenty-sixth edition of the United Nations population estimates and projections. It presents population estimates from 1950 to the present for 235 countries or areas, underpinned by analyses of historical...

Significance This study provides information on sex ratio at birth (SRB) reference levels and SRB imbalance. Using a comprehensive database and a Bayesian estimation model, we estimate that SRB reference levels are significantly different from the commonly assumed historical norm of 1.05 for most regions. We identify 12 countries with strong statis...

This web appendix formed part of the original submission and has been peer reviewed. The journal post it as supplied by the authors. Supplement to: Chao, F., Gerland, P., Cook, A.R. and Alkema, L., 2019. Systematic assessment of the sex ratio at birth for all countries and estimation of national imbalances and regional reference levels. Proceeding...

SRB database for all countries over time. Dataset S1: SRB database formed part of the original submission and has been peer reviewed. The journal post it as supplied by the authors. Supplement to: Chao, F., Gerland, P., Cook, A.R. and Alkema, L., 2019. Systematic assessment of the sex ratio at birth for all countries and estimation of national im...

National SRB annual estimates and 95% uncertainty intervals, 1950–2017. Dataset S2: national SRB annual estimates and 95% uncertainty intervals, 1950–2017, formed part of the original submission and has been peer reviewed. The journal post it as supplied by the authors. Supplement to: Chao, F., Gerland, P., Cook, A.R. and Alkema, L., 2019. System...

Global and regional SRB annual estimates and 95% uncertainty intervals, 1950–2017. Dataset S3: global and regional SRB annual estimates and 95% uncertainty intervals, 1950–2017, formed part of the original submission and has been peer reviewed. The journal post it as supplied by the authors. Supplement to: Chao, F., Gerland, P., Cook, A.R. and Al...

National Annual number of Missing Female Births (AMFB) estimates and 95% uncertainty intervals for the 12 countries with strong statistical evidence of SRB inflation, 1970–2017. Dataset S4: national Annual number of Missing Female Births (AMFB) estimates and 95% uncertainty intervals for the 12 countries with strong statistical evidence of SRB inf...

Mortality databases have been established for developed countries and effectively used for various purposes. For developing countries of which the deaths counted 78% that of the world in 2010–2015, however, reliable life tables can hardly be found. Indirect estimates of life tables using empirical data on child and adult mortality are available for...

The slides were presented on Apr 26th, 2018, in the 2018 Population Association of America Annual Meeting, Denver, CO, USA.

We implemented Bayesian methods for probabilistic sex ratio at birth (SRB) estimation and projection for all countries based on an extensive database with data from vital registration systems, censuses, and surveys. We identified countries at risk of SRB inflation due to sex-selective abortion in the past/current/future. We modeled SRB regional bio...

Background: Documentation of the demographic and geographical details of changes in cause-specific neonatal (younger than 1 month) and 1-59-month mortality in India can guide further progress in reduction of child mortality. In this study we report the changes in cause-specific child mortality between 2000 and 2015 in India. Methods: Since 2001,...

We merge two methodologies, prospective measures of population aging and probabilistic population forecasts. We compare the speed of change and variability in forecasts of the old age dependency ratio and the prospective old age dependency ratio as well as the same comparison for the median age and the prospective median age. While conventional mea...

Objective: To compare the 2016 United Nations Programme on HIV/AIDS (UNAIDS) modelled estimates of adult mortality in sub-Saharan Africa to empirical estimates. Design: Age-specific mortality rates were obtained from nationally representative sibling survival data, recent household deaths and vital registration, and directly compared with UNAIDS...

Background: We consider the problem of probabilistic projection of the total fertility rate (TFR) for subnational regions. Objective: We seek a method that is consistent with the UN's recently adopted Bayesian method for probabilistic TFR projections for all countries and works well for all countries. Methods: We assess various possible method...

We consider the problem of probabilistic projection of the total fertility rate (TFR) for subnational regions. We seek a method that is consistent with the UN's recently adopted Bayesian method for probabilistic TFR projections for all countries, and works well for all countries. We assess various possible methods using subnational TFR data for 47...

The poster was presented on Jun 13th, 2016, in the World Meeting of International Society for Bayesian Analysis, Sardinia, Italy.

The slides were presented on Mar 31st, 2016, in the 2016 Population Association of America Annual Meeting, Washington, DC, USA.

Under normal circumstances, the sex ratio at birth (SRB) has been reported to vary between 1.04 and 1.07. But gender discrimination and other factors associated with the SRB can result in different SRB levels. While SRB estimates have been published for various countries and periods, a systematic assessment of SRBs for all countries over time using...

We show that Bayesian population reconstruction, a recent method for estimating past populations by age, works for data of widely varying quality. Bayesian reconstruction simultaneously estimates age-specific population counts, fertility rates, mortality rates, and net international migration flows from fragmentary data, while formally accounting f...

The UN released official probabilistic population projections (PPP) for all countries for the first time in July 2014. These were obtained by projecting the period total fertility rate (TFR) and life expectancy at birth (e 0) using Bayesian hierarchical models, yielding a large set of future trajectories of TFR and e 0 for all countries and future...

Demographic forecasts are inherently uncertain. Nevertheless, an appropriate description of this uncertainty is a key underpinning of informed decision making. In recent decades various methods have been developed to describe the uncertainty of future populations and their structures, but the uptake of such tools amongst the practitioners of offici...

Background: As child mortality decreases rapidly worldwide, premature adult mortality is becoming an increasingly important contributor to global mortality. Any possible worldwide reduction of premature adult mortality before the age of 70 years will depend on progress in India. Indian districts increasingly have responsibility for implementing pub...

The United Nations publishes projections of populations around the world and breaks these down by age and sex. Traditionally, they are produced with standard demographic methods based on assumptions about future fertility rates, survival probabilities, and migration counts. Such projections, however, were not accompanied by formal statements of unc...

Background As child mortality decreases rapidly worldwide, premature adult mortality is becoming an increasingly important contributor to global mortality. Any possible worldwide reduction of premature adult mortality before the age of 70 years will depend on progress in India. Indian districts increasingly have responsibility for implementing publ...

Summary Background In 2000, world leaders agreed on the Millennium Development Goals (MDGs). MDG 4 called for a two-thirds reduction in the under-5 mortality rate between 1990 and 2015. We aimed to estimate levels and trends in under-5 mortality for 195 countries from 1990 to 2015 to assess MDG 4 achievement and then intended to project how variou...

Demographic data suffer from sampling errors and from biases arising from coverage and content errors that may be systematic and noncompensating. Common and problematic errors for demographic estimation are those affecting the reporting of age, parity, and deaths. Age misreporting affects population counts and vital rates. Techniques of data evalua...

The United Nations released official probabilistic population projections (PPP) for all countries for the first time in July 2014. These were obtained by projecting the period total fertility rate (TFR) and life expectancy at birth ($e_0$) using Bayesian hierarchical models, yielding a large set of future trajectories of TFR and $e_0$ for all count...

Bradshaw and Brook (1) conclude that a substantial slowing of global population growth is infeasible over this century short of drastic reductions in fertility, and therefore could not contribute much to lessening pressure on the environment. However, their methodology is too crude to produce credible results.

Nicholas Kassebaum and colleagues1 noted that maternal deaths have decreased less rapidly worldwide between 1990 and 2010 than reported by the UN agencies. They attribute this difference partly to higher UN estimates of all-cause reproductive-age mortality, especially in west Africa. They state that the UN estimates almost exclusively uses child mo...

Gerland and You comment specifically on the perspective paper from Fink. In their view, with millions of children still at risk of dying of preventable causes, maternal, newborn and child survival must remain at the heart of the post-2015 global development agenda. It is fundamental for everyone to be aware that the necessary knowledge and technolo...

The United Nations (UN) recently released population projections based on data until 2012 and a Bayesian probabilistic methodology. Analysis of these data reveals that, contrary to previous literature, the world population is unlikely to stop growing this century. There is an 80% probability that world population, now 7.2 billion people, will incre...

Preparation of the base population plays a substantial role in the accuracy of projections. This paper reviews analytical strategies involved in the preparation of the UN World Population Prospects (WPP) to reconcile existing discrepancies between data sources and derive robust estimates of population counts, distribution, and demographic changes....

The United Nations regularly publishes projections of the populations of all the world's countries broken down by age and sex. These projections are the de facto standard and are widely used by international organizations, governments and researchers. Like almost all other population projections, they are produced using the standard deterministic c...

Background: The United Nations (UN) produces population projections for all countries every two years. These are used by international organizations, governments, the private sector and researchers for policy planning, for monitoring development goals, as inputs to economic and environmental models, and for social and health research. The UN is con...

The original version of Bayesian reconstruction, a method for estimating age-specific fertility, mortality, migration and population counts of the recent past with uncertainty, produced estimates for female-only populations. Here we show how two-sex populations can be similarly reconstructed and probabilistic estimates of various sex ratio quantiti...

Background: Eastern and South-Eastern Asian countries have witnessed a marked decline in old age mortality in recent decades. Yet no studies have investigated the trends and patterns in old age mortality and cause-of-death in the region. Objective: We reviewed the trends and patterns of old age mortality and cause-of-death for countries in the regi...

A Bayesian approach for probabilistic population projections has recently been used by the United Nations Population Division in the preparation of the 2012 revision of the World Population Prospects. The methods have been implemented in publicly available open-source software as a collection of R packages. In this paper, we demonstrate how to easi...

Using both UN and other empirical (subregional) fertility data, this paper aims at presenting the contours of the timing and pace of fertility transition in Asia.

Urbanization has greatly altered the distribution of world’s cities. We use the 2011 Revision of the World Urbanization Prospects, the largest time series city database with most consistent definition, to investigate growth trajectories of world’s cities by major area and city size from 1950 to 2010. We found that while the number of cities has bee...

Eastern and South-Eastern Asia has witnessed a marked decline in old age mortality in recent decades. Yet no studies have investigated the trend and patterns in overall morality and cause-of-death at older ages. We present data from the 2010 Revision of the World Population Prospects on old age mortality in terms of life expectancy at age 65, age-s...

We use data from the 2009 World Urbanization Prospects database and other sources to estimate trends in the number, distribution, and movement of Chinese cities and centroids since 1950. China’s cities have witnessed a rapid growth with a difference between coastal cities and inland ones. China’s cities tend to be more evenly distributed after 1980...

The Population Division is responsible for the monitoring of demographic trends since the 1950s for all countries and areas in the world. The regular assessment of levels and trends in demographic components, and population estimates critically relies on the availability of census data, and in particular of basic tabulations providing data disaggre...

In developed countries, mortality decline is decelerating at younger ages and accelerating at old ages, a phenomenon we call "rotation." We expect that this rotation will also occur in developing countries as they attain high life expectancies. But the rotation is subtle and has proved difficult to handle in mortality models that include all age gr...

The preparation of the base population for projections plays a substantial role on the accuracy of short-term projection quantities. This paper reviews several analytical strategies used by UN analysts to derive robust estimates of demographic changes (especially for fertility and mortality) by age and sex, and to reconcile existing discrepancies b...

We extend Bayesian population reconstruction, a recent method for estimating past populations by age with fully probabilistic statements of uncertainty. It simultaneously estimates age-specific population counts, vital rates and net migration from fragmentary data while formally accounting for measurement error. As inputs, it takes initial bias-red...

We propose a Bayesian hierarchical model for producing probabilistic forecasts of male period life expectancy at birth for all the countries of the world to 2100. Such forecasts would be an input to the production of probabilistic population projections for all countries, which is currently being considered by the United Nations. To evaluate the me...