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  1. 1

    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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  2. 2

    [Reconciling censal and inter-censal data and determination of the population base] Conciliacion censal y determinacion de la poblacion base.

    Rincon MJ

    In: Metodos para proyecciones demograficas [compiled by] United Nations. Centro Latinoamericano de Demografia [CELADE]. San Jose, Costa Rica, Centro Latinoamericano de Demografia, 1984 Nov. 13-42. (Centro Latinoamericano de Demografia [CELADE] Series E, No. 1003)

    This work describes procedures used by the Latin American Demographic Center (CELADE) for establishing a base population for projection in quinquennial age groups by means of evaluation of population censuses and reconciliation of demographic data for 2 or more intercensal periods. Demographic reconciliation refers to the array of procedures through which the degree of coverage of successive censuses is evaluated; age and sex distributions resulting from incomplete coverage, differential omission, and poor age reporting are corrected; the demographic dynamics of intercensal periods are made coherent with estimates of mortality, fertility, and migration from all available sources; and a base population for population projection is established. There are no fixed rules for evaluation and reconciliation of census data, because the history and quality of data collection in each country are unique. The compensatory equation, in which 2 or more population censuses are reconciled in regard to fertility, mortality, and international migration in intermediate years usually in terms of age cohorts, is an indispensable tool for demographers in developing countries. The need to add children born in the years between censuses and the different types of errors typifying different age groups means that the process of census reconciliation should be carried out separately for at least 3 age groups: children under 5, the 5-9 year cohort, and those over 10 years of age. The age group 0-4 is often the most seriously underestimated. Because the age group 5-9 years is often the best enumerated in Latin American population censuses, it can serve as the basis for correction of the population aged 0-4. The data required include the population aged 5-9 in single years in the last census, the deaths in children under 10 by year of birth and age at death in single years, and the annual number of births in the 10 years preceding the last census. Data from Panama illustrate that the results of this technique are not always acceptable, in which case correction of the 0-4 cohort may be accomplished by means of correction of births and deaths using indirect methods. Corrections for the 5-9 cohort, if required, can be made in a similar manner to that for the youngest group. Evaluation and correction of errors of omission and misreporting of age of the population over 10 is the most difficult because data sources are most often inadequate, these age groups have the greatest age and sex differentials and poorest age reporting, and are most likely to be effected by emigration. All available data should be utilized to produce a group of alternative estimates for each cohort based on diverse basic data and assumptions about such variables as the sex ratios for age agroups. The most likely values must then be selected or calculated. The process by which census results from 1950-80 were used to estimate the base population for a projection by components in Panama illustrates the procedure used by CELADE.
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  3. 3

    Handbook on population projections.

    Kunofsky J

    San Francisco, California, Sierra Club, 1982 Jan. 153 p.

    Designed for environmental and community activists who want to understand population projections, this handbook provides information on the following: ways of talking about population, i.e., censuses, estimates, forecasts, projections, and predictions; evaluating projections; policy debates; projections and wastewater--a case study of federal projections policy, types of population projections (projection methodologies, i.e., extrapolation, land use models, demographic models, econometric models, and ratio methods; geographic scope of projections; subject of projections; short-term and long-term projections; dissaggregating projections; and special information and ad hoc adjustments); how projections are developed (fertility, mortality, migration to the US and within the country, projections and policy, and zero population growth and determining if it has been reached); common errors; and the cast of characters (government agencies that prepare national or subnational projections, private groups that prepare projections, other groups active in the politics of projections, and regular publications and newsletters). Recently, the "politics of population projections" has intensified considerably, with more local governments and interest groups recognizing the power of projections. It is this handbook's goal to facilitate an individual's participation in these local and state debates. The basic idea of a projection done by extrapolation is the assumtpion that a trend in the past will continue into the future. 2 common types of extrapolations are the linear and the exponential. When examining a region for which data on land parcels is available, zoning and the current rate and types of housing construction can be used to projct the number of households. The demographic model breaks population growth into components of fertility, mortality, and migration, and further breaks down fertility and mortality by age, and migration into immigration and emigration. Econometric models of population change are predicated upon a presumed relationship between job availability and migration to or from an area. Ratio methods are frequently used to project population for areas lacking adequate data for using other methods. Projections for the world and for individual countries are prepared by the UN, by academic demographers, and by individual governments. In the US, projections for the world, for countries (including the US, and for individual states) are prepared by subunits of the Bureau of the Census.
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