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  1. 1
    Peer Reviewed

    The Spectrum projection package: improvements in estimating mortality, ART needs, PMTCT impact and uncertainty bounds.

    Stover J; Johnson P; Zaba B; Zwahlen M; Dabis F; Ekpini RE

    Sexually Transmitted Infections. 2008; 84(Suppl 1):i24-i30.

    The approach to national and global estimates of HIV/AIDS used by UNAIDS starts with estimates of adult HIV prevalence prepared from surveillance data using either the Estimation and Projection Package (EPP) or the Workbook. Time trends of prevalence are transferred to Spectrum to estimate the consequences of the HIV/AIDS epidemic, including the number of people living with HIV, new infections, AIDS deaths, AIDS orphans, treatment needs and the impact of treatment on survival. The UNAIDS Reference Group on Estimates, Modelling and Projections regularly reviews new data and information needs and recommends updates to the methodology and assumptions used in Spectrum. The latest update to Spectrum was used in the 2007 round of global estimates. Several new features have been added to Spectrum in the past two years. The structure of the population was reorganised to track populations by HIV status and treatment status. Mortality estimates were improved by the adoption of new approaches to estimating non-AIDS mortality by single age, and the use of new information on survival with HIV in non-treated cohorts and on the survival of patients on antiretroviral treatment (ART). A more detailed treatment of mother-to-child transmission of HIV now provides more prophylaxis and infant feeding options. New procedures were implemented to estimate the uncertainty around each of the key outputs. The latest update to the Spectrum program is intended to incorporate the latest research findings and provide new outputs needed by national and international planners.
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  2. 2

    Population trends since 1954.

    Zlotnik H

    Genus. 2005 Jul-Dec; 61(3-4):111-140.

    At the end of 1951, in the first issue of the Population Bulletin, the United Nations published an article on the past and future growth of world population (United Nations, 1951). The article provided a "long-term view" of future population growth by projecting the population by groups of countries from 1950 to 1980. According to this first set of estimates and projections issued by the United Nations, the world population, which was estimated to be 2.4 billion in mid-1950, would increase by at least half a billion and at most 1.2 billion over the next 30 years, producing for 1980 a range of 3 billion to 3.6 billion people, with a "medium" value of 3.3 billion. A further scenario obtained by maintaining constant the vital rates estimated for the late 1940s produced a world population of 3.5 billion (table 1), The proceedings of the 1954 World Population Conference held in Rome included another set of population projections, updating the work published in 1951. The major difference between the two sets lies on an upward adjustment of the 1950 population of Asia that resulted in a world total closer to 2.5 billion and led to a larger population in 1980 (3.6 billion in the medium variant). Today, with the benefit of hindsight, we estimate that the world's population in 1950 was slightly over 2.5 billion and that it increased by 1.9 billion over the next 30 years, to reach 4.4 billion by 1980, a value higher than the highest projected at the time of the 1954 Conference. In reviewing past demographic trends, this paper will compare them with those expected by United Nations demographers in the 1950s and 1960s in order to understand better their assessment of how the demographic transition would proceed. (excerpt)
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  3. 3

    Fertility rates and population projections: why the United Nations low population projection is best. Draft.

    Seckler D; Cox G

    [Unpublished] 1994 Mar 23. [28] p.

    This paper stems from study on world food needs in the next century. Of course in a study of this nature population projections are essential. The writer used the United Nations medium population projections, illustrated in figure 1, as an authoritative source. Like everyone else of whom we are aware, the author assumed that the United Nations "medium" projection is the best estimate, in the sense of highest probability, in the opinion of the United Nations population experts. Since the medium projection closely corresponds to the World Bank's population projection (they provide only one) through to 2025 the assumption is further justified--and, apparently, supported by the independent opinion of the World Bank experts. (excerpt)
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  4. 4

    Preparing migration data for subnational population projections.

    Speare A

    New York, New York, United Nations, 1992. vii, 46 p. (ST/ESA/SER.A/127)

    Methods pertaining to the preparation of migration data for subnational population projections as of 1992 are explained. A brief review of sources of data for migration projections (censuses, surveys, and registration data) reveals that the requirements are base period estimates of the level or rate of migration between regions, estimates of the age and sex distribution of migrants, and any indicators that show likely future trends. In a discussion of the measurement of the volume of migration from census date, data on residence at a fixed prior time, estimates based on previous place of residence and duration of residence, and estimates of net migration of census survival/ratio methods are relevant. Estimates of the distribution of migrants by age and sex are explained based on different age and sex data: on place of residence at a fixed prior date, on place of previous residence and duration of residence, on age distributions from surveys, and from registers. Also explained is the use of model migration schedules when there is little or no information about age. Baseline migration projections for future estimates which are reasonable and account for variable rates of migration by region are discussed. The objectives desired are sometimes contradictory in that using a long time frame in order to average out random or abnormal fluctuations conflicts with continuing recent nonrandom or unusual changes so that emergent trends will be projected; objectives are also to use the most recent data available which account for shifts in migration patterns and to ensure convergence of migration rates toward equilibrium at some future point. Alternative strategies are provided as well as adjustments to provide consistent results. Adjustments involve the projection of numbers of migrants rather than rates, the use of out-migrant data on destination to adjust in-migration, and the scaling of in-migration to equal out-migration. Recommendations for data collection are presented. Internal migration data are best served by census data which asks the question about place of residence at a fixed prior time preceding the census and with a time interval designation that is of interest for projections. Single year of age and prior year questions and 5 years before are desired due to the need for short-range projections and planning. The 5-year prior place of residence question must be available by current region of residence and age and sex. Specific examples of multiregional projections are included.
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  5. 5

    South Asia's future population: are there really grounds for optimism?

    Leete R; Jones G

    International Family Planning Perspectives. 1991 Sep; 17(3):108-13.

    South Asia consisting of Bangladesh, India, Nepal Pakistan, and Sri Lanka, claims 1/5 to total world population with expected population growth of at least 200 million by the year 2000. Taking issue with assumptions behind World Bank (WB) and United Nations (UN) population projections for the region, the authors make less optimistic assumptions of country fertility and mortality trends when running population projections for the region. Following discussion of methodological issues for and analysis of population projections, the paper's alternate assumptions and projection results are presented and discussed. Projections were made for each country of the region over the period 1985-2010, based on assumptions that only very modest fertility declines and improvements in life expectancy would develop over most of the 1990s. South Asian population would therefore grow from over 1 billion in 1985, to 1.4 billion by 2000, and almost 1.8 billion by 2010. Overall slower fertility decline than assumed for the UN and WB projections point to larger population growth with momentum for continued, larger growth through the 21st century. Rapid, substantial population growth as envisioned by these projections will impede movement toward an urban-industrial economy, with a burgeoning labor force exceeding the absorptive capacity of the modern sector. Job seekers will pile up in agriculture and the informal sector. Demands upon the government to deliver education and health services will also be extraordinarily high. High-tech niches will, however, continue expanding in India and Pakistan with overall negative social effects. Their low demand for labor will exacerbate income disparities, fuel interpersonal, interclass, and interregional tensions, and only contribute to eventual ethnic, communal, and political conflict. Immediate, coordinated policy is urged to achieve balanced low mortality and low fertility over the next few decades.
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  6. 6

    Projecting mortality for all countries.

    Bulatao RA; Bos E; Stephens PW; Vu MT

    Washington, D.C., World Bank, Population and Human Resources Dept., Population, Health, and Nutrition Division, 1989 Dec. [3], 30 p. (Policy, Planning and Research Working Papers, WPS 337)

    On the basis of an assumption of the persistence of current demographic trends, a model is presented for the projection of short-term (1-2 decades) and long-term (1-2 centuries) mortality rates. Essentially, the model refines calculations of male and female life expectancy and takes infant mortality into account in the selection of the appropriate life tables. The analysis of data from developed and developing countries suggests a short-term life expectancy of 82.5 years and a long-term life expectancy of 90 years for women; male life expectancy is 6.7 years lower. For short-term predictions, the rate of change in the preceding 5 years and the proportion of females enrolled in secondary school are most significant. In terms of infant mortality, the rate is expected to decline to 6/1000 in the short-term and 3/1000 in the long- term. A split life table approach is then used, in which the infant mortality rate determines the level to select for mortality at the younger ages and life expectancy is the basis for level selection at the older ages. Application of this projection approach to 8 countries-- Zaire, Bolivia, Ghana, Pakistan, Thailand, Poland, Costa Rica, and Norway--produced mortality estimates that were within 2 percentage points of existing estimates. Infant mortality projections show a greater deviation, with faster falls than suggested by current World Bank estimates. A rapid mortality decline assumption allows life expectancy to be up to 6% higher in 1985-2100, the crude death rate up to 30% lower, and the infant mortality rate up to 50% lower, resulting overall in a population 8% above that expected under conditions of a medium decline. A slow decline pattern allows life expectancy to be 10% lower, the crude death rate up to 50% higher, and the infant mortality rate up to 170% higher than under conditions of medium mortality declines and produces a 13% population decline.
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