Probabilistic population projections for countries with generalized HIV/AIDS epidemics

In 2015, the United Nations (UN) issued probabilistic population projections for all countries up to 2100, by simulating future levels of total fertility and life expectancy and combining the results using a standard cohort component projection method. For the 40 countries with generalized HIV/AIDS epidemics, the mortality projections used the Spectrum/Estimation and Projection Package (EPP) model, a complex, multistate model designed for short-term projections of policy-relevant quantities for the epidemic. We propose a simpler approach that is more compatible with existing UN projection methods for other countries. Changes in life expectancy are projected probabilistically using a simple time series regression and then converted to age- and sex-specific mortality rates using model life tables designed for countries with HIV/AIDS epidemics. These are then input to the cohort component method, as for other countries. The method performed well in an out-of-sample cross-validation experiment. It gives similar short-run projections to Spectrum/EPP, while being simpler and avoiding multistate modelling.     

HIV and population dynamics: A general model and maximum-likelihood standards for East Africa

In high-prevalence populations, the HIV epidemic undermines the validity of past empirical models and related demographic techniques. A parsimonious model of HIV and population dynamics is presented here and fit to 46,000 observations, gathered from 11 East African populations. The fitted model simulates HIV and population dynamics with standard demographic inputs and only two additional parameters for the onset and scale of the epidemic. The underestimation of the general prevalence of HIV in samples of pregnant women and the fertility impact of HIV are examples of the dynamic interactions that demographic models must reproduce and are shown here to increase over time even with constant prevalence levels. As a result, the impact of HIV on population growth appears to have been underestimated by current population projections that ignore this dynamic.     

Population Projections and Demographic Knowledge in France and Great Britain in the Postwar Period

This study examines how official national population projections—a key mechanism for the production and dissemination of demographic knowledge—contributed to differing interpretations of population and fertility trends in France and Great Britain in the decades following World War II, despite these countries' similar fertility rates during most of this period. Projections presented different visions of the demographic future in the two countries. In France, publication of multiple variants emphasized future contingency, with low variants illustrating future population decline due to prolonged below‐replacement fertility. In Britain, publication of a single variant, assuming near‐replacement‐level fertility rates, projected moderate growth. National population projections thus created divergent representations of the two countries' demographic futures: an ever‐present threat of population decline in France, and a reassuring image of stability in Britain. Two principal mechanisms that contributed to cross‐national differences in population projections—national demographic history and institutional configurations—are discussed.     

Accounting for migration in cohort-component projections of state and local populations

Migration is the most difficult component of state and local population growth to forecast accurately because it is more volatile than either births or deaths, and subject to much larger fluctuations within a short period of time. In addition, migration rates can be based on several different measures of migration and the base population. The choice of the appropriate base population has received little attention from demographic researchers, but can have a tremendous impact on population projections. In this article, I develop three different models for projecting migration, each using a different denominator for migration rates. Population projections for ten states are made, using identical data and cohort component techniques, except for the different formulations of migration rates. Differences among the three sets of projections are noted, and conclusions are drawn regarding their usefulness as forecasts of population growth.     

Has the HIV Epidemic Peaked?

This study reviews the highly diverse regional and country patterns of HIV epidemics and discusses possible causes of the geographic variation in epidemic sizes. Past trends and projections of the epidemics are presented and the peak years of epidemics are estimated. The potential future impact of new prevention technologies is briefly assessed. A final section summarizes the future impact of the epidemic on key demographic variables. The main finding of this analysis is that the HIV epidemic reached a major turning point over the past decade. The peak years of HIV incidence rates are past for all regions, and the peaks of prevalence rates are mostly in the past except in Eastern Europe, where they are expected to peak in 2008. But owing in part to the life‐prolonging effect of antiretroviral therapy and to sustained population growth, the absolute number of infected individuals is expected to keep growing slowly in sub‐Saharan Africa and to remain near current levels worldwide, thus posing a continuing challenge to public health programs. No country is expected to see a decline in its population size between 2005 and 2050 that is attributable to high mortality related to AIDS.     

U.S. Family Household Momentum and Dynamics: An Extension and Application of the ProFamy Method

The classic headship-rate method for demographic projections of households is not linked to demographic rates, projects a few household types without size, and does not deal with household members other than heads. By comparison, the ProFamy method uses demographic rates as input and projects more detailed household types, sizes, and living arrangements for all members of the population. Tests of projections from 1990 to 2000 using ProFamy and based on observed U.S. demographic rates before 1991 show that discrepancies between our projections and census observations in 2000 are reasonably small, validating the new method. Using data from national surveys and vital statistics, census microfiles, and the ProFamy method, we prepare projections of U.S. households from 2000 to 2050. Medium projections as well as projections based on smaller and larger family scenarios with corresponding combinations of assumptions of marriage/union formation and dissolution, fertility, mortality, and international migration are performed to analyze future trends of U.S. households and their possible higher and lower bounds, as well as enormous racial differentials. To our knowledge, the household projections reported in this article are the first to have found empirical evidence of family household momentum and to have provided informative low and high bounds of various indices of projected future households and living arrangements distributions based on possible changes in demographic parameters.     

The United Nations on World Population in 2300

The Population Division of the United Nations biennially issues detailed population estimates and projections covering the period 1950–2050. The most recent revision of these estimates and projections, the 2002 assessment, was released in February 2003. At irregular intervals, the Population Division also publishes long‐range projections. The most recent of these, covering the period up to 2150, was issued in 2000, based on the 1998 assessment. On 9 December 2003, the Population Division released the preliminary report on a new set of long‐range projections, dovetailing with the 2002 assessment, that extend over a much longer time span: up to 2300 ( http://www.un.org/esa/population/publications/longrange2/longrange2.htm ). Unlike previous long‐range projections, which, apart from China and In‐dia, were prepared for large regional groupings only, the new projections are elaborated separately for 192 countries. Given the enormous uncertainties of the character of demographic trends over such an extended period, the information content of these projections is somewhat elusive. However, they are expected to be used to provide the demographic input for long‐range models of global climate change. Long‐range population projections also serve to demonstrate the unsustainability of certain seemingly plausible assumptions as to the future course of particular demographic parameters. In the present case, for example, the high‐fertility projection, reflecting a sustained total fertility rate at the relatively modest level of 2.35, by 2300 would yield a population of some 32 billion in the countries now classified as less developed. Or, in a yet more extreme exercise 0/reductio ad absurdum, maintaining constant fertility at present rates would result in a population size of some 120 trillion in the countries now classified as least developed. Apart from the “high fertility” and “constant fertility” models just cited, the projections are calculated for three additional instructive variants: “low fertility,”“medium fertility,” and “zero growth.” Underlying each of the five variants is a single assumption on mortality change: expectation of life at birth creeping up, country‐by‐country, to a 2300 level ranging between 88 and 106 years. International migration is set at zero throughout the period 2050‐2300 in each variant. Thus the projections are unabashedly stylized and surprise‐free, providing a simple demonstration of the consequences, in terms of population size and age structure, of clearly stated assumptions on the future course of demographic variables. Reproduced below is the Executive Summary of the preliminary report on the UN long‐range projections presented to a UN technical working group on long‐range projections at its December 2003 meeting in New York and slightly revised afterward. A full final report on this topic by the Population Division of the Department of Economic and Social Affairs of the United Nations Secretariat will be published later in 2004.     

Data quality and accuracy of United Nations population projections, 1950-95

Between 1951 and 1998, the United Nations (UN) published 16 sets of population projections for the world, its major regions, and countries. This paper reports the accuracy of the projection results. I analyse the quality of the historical data used for the base populations of the projections, and for extrapolating fertility and mortality. I study also the impact this quality has had on the accuracy of the projection results. Results and assumptions for the sets of projections are compared with corresponding estimates from the UN 1998 Revision for total fertility and life expectancy at birth, total population, and the projected age structures. The report covers seven major regions (Africa, Asia, the former USSR, Europe, Northern America, Latin America, and Oceania) and the largest ten countries of the world as of 1998 (China, India, the USA, Indonesia, Brazil, Pakistan, Russia, Japan, Bangladesh, and Nigeria).     

Crossovers that link populations with the same vital rates

"In this paper, we consider crossovers of demographic density distributions from...populations that have the same fertility and mortality rates. We focus on observed populations and their associated stationary and stable models, and on proportional distributions of persons, births, deaths and reproductive values....Three different populations were selected to represent a range of demographic behavior. Those populations are Japan 1963, a low mortality, low fertility population; Togo 1961, a high mortality, high fertility population; and the United States 1919-1921, a population whose fertility and mortality are intermediate."     

Population projections: states, 1995 - 2025

All states will have more people in the future, especially in the south and west, while population aging occurs as the baby boomers age. This report identifies population changes projected to affect the US's 50 states and District of Columbia during 1995-2015. Basic assumptions for state population projections are presented with regard to population, births, deaths, net international migration, and net internal migration. The methodology used to produce the report is also described. Total population and net change is presented in tabular format for each state over the period. These data are used as the basic input to many federal, state, and local projection models which produce detailed statistics on education, economic factors, labor force, health care, voting, and other subjects. State differentials in fertility and mortality are also projected to widen, reflecting the concentration of race and ethnic groups with high fertility in some states and differential migration patterns.     

Demographic Consequences of the ‘Closing the Gap’ Indigenous Policy in Australia

The demography of Indigenous Australians is distinguished from that of other Australians by relatively high mortality and fertility leading to very different composition by age. This is beginning to change as movement towards a convergence in vital rates is observed. In the meantime, the Australian government has established targets for Indigenous socioeconomic outcomes that simultaneously impact on, and are affected by, the course of demographic change. This paper examines the relationship between these targets and projected Indigenous demographic outcomes that arise from incipient population ageing. The most likely scenario is movement into an indeterminate period of potential demographic dividend. If demand for Indigenous labour expands alongside reductions in age dependency this could provide for dramatic improvement in Indigenous economic circumstances. However, caution is warranted as disparities in adult mortality require long-term solutions and movement into a second phase of demographic transition appears likely to be delayed.     

Comparison of microcomputer programs for making population projections: an update

"There are many programs for making population projections now available for use with microcomputers. This article reviews six of approximately 15 microcomputer population projection programs. Each program is compared to a standard set of criteria relating to such items as hardware and software requirements, input data requirements and specification of assumptions, methodology and documentation, and summary output indicators. Numerical results from projections of six test data sets reflecting different assumptions about mortality, fertility, and migration are compared. Qualitative comments are included for describing special features and for making an overall assessment of each program." (SUMMARY IN FRE)     

Comparison of microcomputer programs for making population projections: An update

There are many programs for making population projections now available for use with microcomputers. This article reviews six of approximately 15 microcomputer population projection programs. Each program is compared to a standard set of criteria relating to such items as hardware and software requirements, input data requirements and specification of assumptions, methodology and documentation, and summary output indicators. Numerical results from projections of six test data sets reflecting different assumptions about mortality, fertility, and migration are compared. Qualitative comments are included for describing special features and for making an overall assessment of each program.     

The Census Bureau on Prospects for US Population Growth in the Twenty‐First Century

The U.S. Census Bureau periodically releases projections of the US resident population, detailed by age, sex, race, and Hispanic origin. The most recent of these, issued 13 January 2000, for the first time extend to the year 2100 and also include information on the foreign‐bom population. (Earlier projections were carried up to 2080.) The extensive tabulations presenting the new set, and detailed explanation of the methodology and the assumptions underlying the projections, are accessible at the Census Bureau's web site: http://www.census.gov . A brief summary of some of the main results of these projections is reproduced below from United States Department of Commerce News, Washington, DC 20230. (The Census Bureau is an agency of the Department of Commerce.) Uncertainties as to future trends in fertility, mortality, and net migration over a period of some 100 years are very great, as is illustrated by the massive difference in the projected size of the population for 2100 in the three variants produced. The “middle” projected population figure of 571 million (which represents a growth of some 109 percent over its current level) is bracketed by “lowest” and “highest” alternative projections of 283 million and 1.18 billion, respectively. With somewhat lesser force, the point also applies to the 50‐year time span considered in the well‐known country‐by‐country projections of the United Nations. These projections are also detailed in three variants: low, middle, and high. The UN projections (last revised in 1998) envisage less rapid growth in the United States during the first part of the twenty‐first century than do the Census Bureau's. The projected population figures for 2050 in the three variants (low, middle, and high) are as follows (in millions):

HIV and fertility in Africa: first evidence from population-based surveys

The historical pattern of the demographic transition suggests that fertility declines follow mortality declines, followed by a rise in human capital accumulation and economic growth. The HIV/AIDS epidemic threatens to reverse this path. We utilize recent rounds of the demographic and health surveys that link an individual woman’s fertility outcomes to her HIV status based on testing. The data allow us to distinguish the effect of own positive HIV status on fertility (which may be due to lower fecundity and other physiological reasons) from the behavioral response to higher mortality risk, as measured by the local community HIV prevalence. We show that although HIV-infected women have significantly lower fertility, local community HIV prevalence has no significant effect on noninfected women’s fertility.     

Countries with Rapid Population Growth and Resource Constraints: Issues of Food,Agriculture, and Development

Recent long‐term demographic projections suggest a fast deceleration of global population growth and the eventual peaking of world population later in this century at about 9.2 billion, roughly 50 percent above the present level. Some low‐income and food‐insecure countries, however, have projected populations in 2050 that are multiples of present ones. In some of these countries agriculture must play a leading role in their development efforts because they have high economic dependence on that sector. For those among them that have scarce agricultural resources, a prima facie case can be made that the high population growth rates projected may not be compatible with the development potential offered by such resources. Their demographic projections may need to be revisited, taking into account such inadequate potential. The global demographic slowdown notwithstanding, the “population explosion”‐related issues pertaining to food and agriculture will not become irrelevant but will be become increasingly localized.     

Alternative Projections of the U.S. population

The U.S. Bureau of the Census recently released a set of population projections that include middle and high projections that we argue are too conservative. The projections discount the possibility of future baby booms and assume slow rates of mortality decline and low levels of immigration. In this article we explore the impact on the size and age composition of the U.S. population of alternative scenarios of plausible fertility, mortality, and immigration assumptions. We conclude that (1) the Census Bureau's highest projection might be interpreted as a reasonable middle projection, (2) a reasonable high projection would yield a U.S. population in 2080 some 300 million persons larger than the Bureau's highest projection, with the population 85 and older more than twice the Bureau's greatest estimate, and (3) uncertainty about the pace of population growth is substantially greater than the Bureau's projections suggest.     

On the derivation of a two-sex stable population model

It is well known that the intrinsic rates of growth derived separately for the males and females in a population, when one assumes the continuation of their respective mortality and fertility experiences, usually turn out to be different. Noting that the phenomenon of human reproduction is a product of the cooperation between the two sexes, we have attempted in this paper to define the sex-age-specific fertility rates as a function not only of age but also of time, where the latter is implicitly introduced in the model through the sex composition of the reproductive population. It has been shown that a stable model can then be defined based on such changing sex-age-specific fertility rates and given sets of unchanging mortality rates. The fertility rates stabilize with time, and the common intrinsic rates of growth for the two sexes are found to lie in the interval generated by the corresponding rates of the two one-sex models. Several other interesting relationships among the parameters of this model have been presented in the paper. Among other alternatives, a least square solution has been presented for the values of sex-age-specific fertility rates that are minimally discrepant with the observed rates but are consistent in terms of the parametric estimates they generate. It is interesting to note that a relatively modest adjustment in the sex-age-specific fertility rates is all that it takes to eliminate the inconsistencies generated by the separate one-sex models.     

Understanding Global Demographic Convergence since 1950

Is the world converging to a single demographic regime? Or are groups of countries following distinct paths through the process of demographic transition? The answers to these questions are pivotal to our understanding of the nature and mechanisms of population change. They are also key elements for deriving the assumptions that should underlie population projections. There has been considerable interest in global demographic convergence during the last decade, with most work drawing on statistical methods that are widely used in economics. This article takes a different approach to most of the existing literature, examining the fertility and mortality trajectories over time that various appropriately defned world regions have followed. The data suggest that five distinct regional histories can be traced in mortality, and three in fertility, and that global convergence has moved more rapidly and unambiguously in fertility than in mortality.