Models for the estimation of the probability of dying between birth and exact ages of early childhood

Abstract This paper develops two models, each of which is designed to estimate the probability of surviving from birth to selected exact ages of early childhood: namely ages two, three and five. The models are designed for use in areas with deficient registration systems. They require, as input, statistics which can be derived from retrospective data supplied by census or survey respondents. The first model, the age model, converts statistics on the proportion dead of children ever born to women in age groups 20-24, 25-29 and 30-34 into estimates of q2, q3 and q5. The second model, the marriage model, converts statistics on the proportion dead of children ever born to women of five-year marriage duration intervals into these estimates. The models can be used independently or simultaneously. These models were developed from data generated by a large number of empirical fertility and mortality schedules. Regression analysis was used to determine the parameter values of the relationships specified, and several sets of equations for estimating values of qa, for a = 2, 3 and 5 comprise the final product of the paper. It should be noted that the conceptual basis for the models was first derived by William Brass. The data generated for the regression analysis provided an opportunity to test the original Brass estimated model. We are able to report that the model performed well over the wide range of fertility and mortality conditions included in the test.     

Estimation of interprovincial migration for Canada from place of birth by residence data, 1951–1961

In Canada, unlike many other countries, birth-residence data by age and sex are available in each of the decennial censuses from 1931 to 1961 which permit the estimation of intercensal net migration for the provinces and regions. After a brief discussion of the basic measures of migration from birth-residence data the paper focusses on the problems and procedures in estimating interprovincial net migration, 1951–1961 for Canada using “the place of birth survival ratio method, ” and it evaluates the estimates thus obtained. The evaluation of the estimates, taking into consideration the inherent limitations of the method and its merits compared with period migration estimates by the census survival ratio method and life table survival ratio method, suggests that the net migration estimates for the Canadian born by the place of birth survival ratio method are probably more reliable than those by the other two methods. One striking finding was that the net migration curves by age obtained from the census survival ratio and place of birth survival ratio estimates were smoother than the curve obtained with the use of the more accurate life table survival ratios. Furthermore, whatever the relative accuracy of net migration may be, the birth-residence approach is capable of furnishing more details about the net migration of the native born than by the standard survival-ratio methods. For the population under age 10 intercensal estimates were directly derived from the place of birth and residence distributions by age.     

A regression approach to estimating the average number of persons per household

In the housing unit method, population is calculated as the number of households times the average number of persons per household (PPH), plus the population residing in group quarters facilities. Estimates of households and the group quarters population can be derived directly from concurrent data series, but estimates of PPH have traditionally been based on previous values or estimates for larger areas. In our study, we developed several regression models in which PPH estimates were based on symptomatic indicators of PPH change. We tested these estimates using county-level data in four states and found them to be more precise and less biased than estimates based on more commonly used methods.     

Estimation of local demographic variation in a flexible framework for population projections

A cohort component projection of local populations based on sex and single year of age offers great value for planning local services, but demands data beyond the detail available. Local fertility, mortality and migration schedules by age and sex must be estimated sensitively to local variation if the results are to be of greater value than simpler methods of projection. Two approaches are compared, using data for the recent past: (a) direct estimation of local area age-specific schedules of fertility, mortality and migration based on data available to the national statistical agency; (b) graduation of national schedules using only local area population estimates by age, total numbers of births, and total numbers of deaths; age-specific migration is indirectly estimated from successive population estimates. These two approaches are compared with a projection using the same rates for each area. The three projections have been implemented for electoral wards in the Fife local government area of Scotland, using the flexible framework provided by POPGROUP software. Persuasive local population projections based on standard data for standard areas are feasible without the regular publication of migration flows.     

Bayesian Estimation of Age-Specific Mortality and Life Expectancy for Small Areas With Defective Vital Records

High sampling variability complicates estimation of demographic rates in small areas. In addition, many countries have imperfect vital registration systems, with coverage quality that varies significantly between regions. We develop a Bayesian regression model for small-area mortality schedules that simultaneously addresses the problems of small local samples and underreporting of deaths. We combine a relational model for mortality schedules with probabilistic prior information on death registration coverage derived from demographic estimation techniques, such as Death Distribution Methods, and from field audits by public health experts. We test the model on small-area data from Brazil. Incorporating external estimates of vital registration coverage though priors improves small-area mortality estimates by accounting for underregistration and automatically producing measures of uncertainty. Bayesian estimates show that when mortality levels in small areas are compared, noise often dominates signal. Differences in local point estimates of life expectancy are often small relative to uncertainty, even for relatively large areas in a populous country like Brazil.     

Evaluation of Alternative Cohort-Component Models for Local Area Population Forecasts

It is generally accepted by demographers that cohort-component projection models which incorporate directional migration are conceptually preferable to those using net migration. Yet net migration cohort-component models, and other simplified variations, remain in common use by both academics and practitioners because of their simplicity and low data requirements. While many arguments have been presented in favour of using one or other type of model, surprisingly little analysis has been undertaken to assess which tend to give the most accurate forecasts. This paper evaluates five cohort-component models which differ in the way they handle migration, four of which are well known, with one—a composite net migration model—being proposed here for the first time. The paper evaluates the performance of these five models in their unconstrained form, and then in a constrained form in which age–sex-specific forecasts are constrained to independent total populations from an extrapolative model shown to produce accurate forecasts in earlier research. Retrospective forecasts for 67 local government areas of New South Wales were produced for the period 1991–2011 and then compared to population estimates. Assessments of both total and age-specific population forecasts were made. The results demonstrate the superior performance of the forecasts constrained to total populations from the extrapolative model, with the constrained bi-regional model giving the lowest errors. The findings should be of use to practitioners in selecting appropriate models for local area population forecasts.     

Revising the Harris-Todaro framework to model labour migration from the Canadian Northern frontier

The Harris-Todaro model of labour migration was developed almost four decades ago, and since has become a classic method of migration analysis in less developed countries. This paper explores the applicability of the Harris-Todaro (HT) framework outside its traditional use, by modelling frontier-metropolis migration in Canada. If appropriate, the framework can potentially be used in other countries with similar regional dichotomies, such as Russia and Australia. The paper argues that the HT model is generally applicable in the context of migration from the resource frontier to large metropolitan areas of the Canadian south, although it requires several modifications. The classic HT model is extended to account for northern labour-force heterogeneity (Aboriginal and Non-Aboriginal), the possibility of having or losing jobs in the declining and undiversified frontier economy, and living cost differentials. Further analysis is focused on Aboriginal migration from isolated northern communities. The plausibility of the modified HT model is demonstrated using an empirical test, in which the model is used to assess migration probabilities of Aboriginal labour migrants. These new insights into the mechanisms of frontier-metropolis migration could provide a better basis for developing planning strategies, aimed to sustain human capital in the Canadian North, and for optimizing welfare policies both in the North and in the South.     

Understanding the demographic implications of climate change: estimates of localized population predictions under future scenarios of sea-level rise

Significant advances have been made to understand the interrelationship between humans and the environment in recent years, yet research has not produced useful localized estimates that link population forecasts to environmental change. Coarse, static population estimates that have little information on projected growth or spatial variability mask substantial impacts of environmental change on especially vulnerable populations. We estimate that 20 million people in the United States will be affected by sea-level rise by 2030 in selected regions that represent a range of sociodemographic characteristics and corresponding risks of vulnerability. Our results show that the impact of sea-level rise extends beyond the directly impacted counties due to migration networks that link inland and coastal areas and their populations. Substantial rates of population growth and migration are serious considerations for developing mitigation, adaptation, and planning strategies, and for future research on the social, demographic, and political dimensions of climate change.     

中国老年人口迁移的选择性

本文利用2005年全国1％人口抽样调查数据,描述老年人口跨地市级迁移的结构特征。研究发现,我国老年人口依旧把经济发达地带、大城市作为主要迁入地,与青壮年人口迁移方向产生同构。城乡老年迁移人口在迁移动机上存在很大的差别,城市户籍老年迁移人口受家庭因素驱动更大,农村户籍老年人的迁移原因更多元。从对迁入地的影响来看,国内老年迁移人口的迁入地过于集中,将对迁入地的社会医疗服务设施等构成巨大的压力。     

An interactive contextual model of migration in Ilocos Norte,the Philippines

This paper develops and estimates an interactive contextual model of migration in Ilocos Norte, the Philippines. It focuses on how contextual features alter the effects of family class status and community development level on the family's migration decisions. The model estimates show a curvilinear relation between class status and migration, but the pattern differs in accordance with the prevalence of migration from the community in the past. In addition, the effects of socioeconomic development and agricultural commercialization patterns vary with context. These results demonstrate the importance of using interactive models for analyzing the contextual influences on migration.     

Subnational migration in the United Kingdom: producing a consistent time series using a combination of available data and estimates

There is no single framework in place in the United Kingdom for collating and harmonizing the data on migration taking place between the subnational administrative units that constitute the home nations, together with the flows of international migration between these areas and the ‘rest of the world’. This paper proposes the construction of complete matrices of subnational migration statistics on an annual basis which can then be used to monitor migration trends throughout the UK in a comprehensive manner. The paper reviews how various ‘known’ flows are estimated by the national statistics agencies and develops estimates to fill in the gaps in the matrices. It then looks at changing patterns of migration in the UK between 2001/2002 and 2010/2011, showing that migration exhibits most activity in the middle of the decade. Flows within the home nations are the most consistent over time, while the patterns of international migration and migration across the borders of the home nations exhibit more substantial change. The latter flows, although relatively small in magnitude, have not previously been studied at the subnational level in any detail. Patterns of subnational internal and international net migration are found to be negatively correlated.     

A cost-benefit model of rural to urban migration in Taiwan

Abstract Migration is a form of human behaviour which has lent itself to careful measurement for a relatively long period of time. In 1885 Ravenstein set forth certain empirical laws concerning the relationship of migration to age and distance which have held up to the present. Since then an abundance of migration data has enabled social scientists to develop more precise models relating the volume or rate of migration to characteristics of the migrants or of the areas of origin and destination. Prominent among these models are the gravity model, the intervening opportunities model, a gravity type model including wage rates and unemployment rates developed by Lowry, and the Cornell mobility model.     

劳动力流动与地区经济增长差距研究

文章借鉴巴罗、萨拉伊马丁和德拉柯兹有关带移民的经济增长模型,并在此基础上对劳动力流动与地区内、地区间经济增长差距的内在关系进行理论推导发现,劳动力流动加快了中国发达地区经济增长收敛速度,而降低了欠发达地区的经济增长收敛速度。通过考察地区间因劳动力流动而导致的人力资本存量变动及相应的潜在产出外溢与滴漏效应冲击,印证了劳动力流动拉大地区差距的结论。作者还估算了近年来劳动力省际流动状况,并进行实证研究。     

Simultaneity bias in migration models: An empirical examination

A number of migration studies have attempted to explain migration that occurred over a given time interval by means of variables defined for the end of the period and/or variables relating to changes that occurred over the period. Since migration may influence end-of-period levels of explanatory variables by influencing the behavior of these variables over the period of migration, simultaneous-equations bias may be inherent in the parameter estimates of the many single-equation, multiple-regression analyses. This study constitutes an empirical examination of qualitative differences in the parameter estimates of five different types of migration models estimated for two different time periods, 1960 and 1970.     

Urban temporary out-migration under economic reforms: Who moves and for what reasons?

Studies of temporary migration in developing countries often focus on rural outmigration and are preoccupied with problems it may bring to cities. Using a unique data set from two surveys conducted in Zhejiang province, China, this paper examines the other side of the coin — temporary migration from urban places — and thereby provides an important complement to studies focusing on rural-urban migration. The analysis identifies three types of temporary migrations: on-business, economic, and family-related. Using multinomial logit model, the analysis suggests that the three types of temporary migration differ significantly from each other in both their causes and migrants' socioeconomic characteristics; so does urban-urban migration from urban-rural migration. The considerable urban-rural temporary migration attests to the fact that temporary migration is not a one-way process; its positive selectivity further indicates that a considerable human capital flows from urban to rural areas through urban-rural temporary migration, which provides rural areas much needed science and technology and becomes an important facilitating factor of rural socioeconomic development.This article is based on a paper, presented at the meetings of the American Sociological Association, Pittsburgh, August 1992.     

Parental survival data: Some results of the application of Ledermann's model life tables

Summary Ledermann's one- and two-parameter model life tables are used in order to summarize and compare adult mortality estimates derived from parental survival data, and also to link parental survival with child survival data. The Ledermann models provide an alternative to the logit model used by Brass and Hill. Examination of life tables derived from actual child and adult mortality estimates reveals that although the two types of models yield similar overall levels of mortality, they show marked differences in the estimated patterns by sex and age. It has not been possible to disentangle completely how much of this divergence is due to the models themselves and how much to inadequacies in the data available. Finally, we question whether it is always wise to establish a full life table from child and adult mortality estimates when these are based on data which refer to different periods of exposure to the risk of dying, without allowance for possible distortions resulting from mortality change.     

Model Migration Schedules: Three Alternative Linear Parameter Estimation Methods

ABSTRACT

Observed schedules of migration rates exhibit strong regularities in age patterns. These regularities may be captured and represented by a mathematical expression known as the multiexponential model migration schedule. Fitting this function to empirical data requires non-linear regression methods and often some experimentation with alternative initial estimates of the parameters. Simpler, linear methods of estimation are adequate for most applications. These may be carried out with hand calculators or simple spreadsheet-based calculations on the computer. Such methods are studied and appear to perform satisfactorily.     

A framework for the study of migration destination selection

This article raises a number of issues that have generally not been addressed in previous studies of migration destination selection. Destination selection is seen as the result of two processes; (1) the sorting among a relatively large number of potential destinations over a lifetime, and (2) the selection among a relatively few (usually one or two) places at the time of the migration decision. Decision rules may differ in the two processes. The actual selection of a destination is based on place utilities derived from a combination of factors including: economic and noneconomic; micro (those attributes unique to one place); and macro (those applicable to larger geographic areas).     

Duration of residence and prospective migration: Further evidence

A basic assumption of the Cornell Mobility Model insofar as it is relevant to inter-community migration is that an individual’s propensity to move is a function of, among other things, his length of residence in the community. Parameters of the functional relationship of migration probabilities to duration status are estimated from migration histories for a sample of residents in Monterrey, Mexico, and compared with estimates reported by P. A. Morrison using data from Amsterdam, The Netherlands. In both data sets a negative nonlinear relation of the probability of migrating to duration status, as well as an interaction between age and duration status, is found. Values of parameters describing the relation within age groups differ sufficiently between the two data sets, however, to suggest that further specification of conditions under which a particular form of functional relation will obtain is necessary if the model is to be useful in migration research.