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At least 19 recordsLinked to original sources
PubMed1983

Improving the accuracy of migration age detail in multiple-area population forecasts.

Population projections are often required for many geographical areas, and must be prepared with maximal computer and minimal analytical effort. At the same time, realistic age detail forecasts require a flexible means of treating age-specific net migration. This report presents a migration projection technique compatible with these constraints. A simplified version of Pittenger's model is used, where future migration patterns are automatically assigned from characteristics of historical patterns. A comparative test of age pattern accuracy for 1970-1980 indicates that this technique is superior to the commonly used plus-minus adjustment to historical rates.

Adolescent↗
PubMed1991

An empirical analysis of the effect of length of forecast horizon on population forecast errors.

Many studies have found that population forecast errors generally increase with the length of the forecast horizon, but none have examined this relationship in detail. Do errors grow linearly, exponentially, or in some other manner as the forecast horizon becomes longer? Does the error-horizon relationship differ by forecasting technique, launch year, size of place, or rate of growth? Do alternative measures of error make a difference? In this article we address these questions using two simple forecasting techniques and population data from 1900 to 1980 for states in the United States. We find that in most instances there is a linear or nearly linear relationship between forecast accuracy and the length of the forecast horizon, but no consistent relationship between bias and the length of the horizon. We believe that these results provide useful information regarding the nature of population forecast errors.

Humans↗
PubMed1997

[Population forecasts 1996: less population growth, increased aging].

"According to the new national population forecasts for the Netherlands for the period 1996-2050, the population size will continue to grow for another three decades. It will reach a maximum of 17.2 million, lower than the maximum according to the previous population forecasts.... The reason for this lower growth is that the assumption with respect to the future level of fertility is revised downwards.... Another adjustment of the forecasts is the assumption that life expectancy at birth will continue to increase until 2050, whereas in the previous forecasts life expectancy was held constant after 2010.... As a consequence of these revised assumptions the percentage of elderly people will increase more strongly." (SUMMARY IN ENG)

Age Distribution↗
PubMed1987

Population forecasts for South Pacific nations using autoregressive models, 1985-2000.

"This paper uses an autoregressive statistical model to forecast population for Fiji, Western Samoa, Tonga, Solomon Islands, and Vanuatu and compares these forecasts with those obtained from other methods. The growth rate of population is predicted to continue to fall in Fiji and Tonga, rise a little for Western Samoa, and rise considerably in Vanuatu and the Solomon Islands. The implications of the forecasts for recent government development plans are also discussed."

Demography↗
PubMed1992

Uncertainty variants of population forecasts.

"When using population forecasts it is important to take into account the degree of uncertainty of the results. For that reason the Netherlands Central Bureau of Statistics publishes low and high variants next to the most probable medium variant.... The width of the interval between the variants is based on an analysis of previous forecast errors. The degree of uncertainty of the various forecast results turns out to vary strongly.... On the basis of a statistical time-series model of forecast errors of total population growth, a confidence interval of total population size can be estimated."

Demography↗
PubMed1984

[Population forecasts in 1980, an analysis of mortality by cause of death].

The methods of projecting future mortality in official forecasts of population growth in the Netherlands are described. In particular, it is noted that the projected sex, age, and marital status specific death rates were not split up by causes of death. An analysis of mortality from 1980 to 1990 is presented, and it is shown that "the life expectancies calculated for extrapolated death rates split up by group of causes of death hardly differ from those where such a split up is not made. According to the figures presented...the differences never exceed 0.2 years. From these figures it cannot be concluded that splitting up the death rates by groups of causes of death in the national population forecasts would lead to significantly different results as far as mortality is concerned." (summary in ENG)

Cause of Death↗
PubMed1985

Uncertain population forecasting.

"Errors in population forecasts arise from errors in the jump-off population and errors in the predictions of future vital rates. The propagation of these errors through the linear (Leslie) growth model is studied, and prediction intervals for future population are developed. For U.S. national forecasts, the prediction intervals are compared with the U.S. Census Bureau's high-low intervals." In order to assess the accuracy of the predictions of vital rates, the authors "derive the predictions from a parametric statistical model and estimate the extent of model misspecification and errors in parameter estimates. Subjective, expert opinion, so important in real forecasting, is incorporated with the technique of mixed estimation. A robust regression model is used to assess the effects of model misspecification."

Americas↗
PubMed1990

The relationship between the length of the base period and population forecast errors.

"The base period of a population forecast is the time period from which historical data are collected for the purpose of forecasting future population values. The length of the base period is one of the fundamental decisions made in preparing population forecasts, yet very few studies have investigated the effects of this decision on population forecast errors. In this article the relationship between the length of the base period and population forecast errors is analyzed, using three simple forecasting techniques and data from 1900 to 1980 for states in the United States. It is found that increasing the length of the base period up to 10 years improves forecast accuracy, but that further increases generally have little additional effect. The only exception to this finding is long-range forecasts of rapidly growing states, in which a longer base period substantially improves forecast accuracy for two of the forecasting techniques."

Americas↗
PubMed1987

Measuring the accuracy of population forecasts.

The accuracy of population projections is discussed, with specific reference to population forecasts for development planning purposes. The author notes that errors in making population forecasts depend on the parameter values used in the calculations, and that such errors can be avoided if the demographic models used are seen not as stochastic but as models with random parameters. "For such models the present article derives estimations of the covariance matrices of forecasts of the social and age composition of the population."

Age Distribution↗
PubMed1991

The impact of forecasting methodology on the accuracy of national population forecasts: evidence from the Netherlands and Czechoslovakia.

"This study considers the accuracy of national population forecasts of the Netherlands and the Czechoslovak Socialist Republic.... We look at the demographic components employed in each forecast, the procedure to extrapolate fertility and the level at which assumptions for each component are formulated. Errors in total population size, fertility, mortality and foreign migration, and age structure are considered. We discuss trends in errors and methodology since 1950 and compare the situations in the two countries. The findings suggest that methodology has only a very limited impact on the accuracy of national population forecasts."

Czechoslovakia↗
PubMed1986

Methods for national population forecasts: a review.

"Three widely used classes of methods for forecasting national populations are reviewed: demographic accounting/cohort-component methods for long-range projections, statistical time series methods for short-range forecasts, and structural modeling methods for the simulation and forecasting of the effects of policy changes. In each case, the major characteristics, strengths, and weaknesses of the methods are described. Factors that place intrinsic limits on the accuracy of population forecasts are articulated. Promising lines of additional research by statisticians and demographers are identified for each class of methods and for population forecasting generally."

Cohort Studies↗
PubMed1986

Population forecasts and confidence intervals for Sweden: a comparison of model-based and empirical approaches.

This paper compares several methods of generating confidence intervals for forecasts of population size. Two rest on a demographic model for age-structured populations with stochastic fluctuations in vital rates. Two rest on empirical analyses of past forecasts of population sizes of Sweden at five-year intervals from 1780 to 1980 inclusive. Confidence intervals produced by the different methods vary substantially. The relative sizes differ in the various historical periods. The narrowest intervals offer a lower bound on uncertainty about the future. Procedures for estimating a range of confidence intervals are tentatively recommended. A major lesson is that finitely many observations of the past and incomplete theoretical understanding of the present and future can justify at best a range of confidence intervals for population projections. Uncertainty attaches not only to the point forecasts of future population, but also to the estimates of those forecasts' uncertainty.

Forecasting↗