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.     

Ethnic population projections for the UK, 2001–2051

This paper reports on projections of the United Kingdom’s ethnic group populations for 2001–2051. For the years 2001–2007 we estimate fertility rates, survival probabilities, internal migration probabilities and international migration flows for 16 ethnic groups and 355 UK areas. We make assumptions about future component rates, probabilities and flows and feed these into our projection model. This model is a cohort-component model specified for single years of age to 100+. To handle this large state space, we employed a bi-regional model. We implement four projections: (1) a benchmark projection that uses the component inputs for 2001; (2) a trend projection where assumptions beyond 2007 are adjusted to those in the UK 2008-based National Population Projections (NPP); (3) a projection that modifies the NPP assumptions and (4) a projection that uses a different emigration assumption. The projected UK population ranges between a low of 63 millions in 2051 under the first projection to a high of 79 million in the third projection. Under all projections ethnic composition continues to change: the White British, White Irish and Black Caribbean groups experience the slowest growth and lose population share; the Other White and Mixed groups to experience relative increases in share; South Asian groups grow strongly as do the Chinese and Other Ethnic groups. The ethnic minority share of the population increases from 13% (2001) to 25% in the trend projection but to only 20% under our modified emigration projection. However, what is certain is that the UK can look forward to be becoming a more diverse nation by mid-century.     

Understanding population projections

This is a general introduction to how population projections are made and used for the consumers of this information. Population projections are computations of what future trends in fertility, mortality and migration of a population might be given set assumptions. They are not actual forecasts. Projections are used by planners in government and business for a clearer understanding of social changes. How to prepare projections, obtain base data, select starting and future levels of rates, variant series, and the mathematics involved are discussed. Assumptions must be carefully checked and chosen, since reliability of the projections depends on assumptions. There are 3 rules of thumb for reliability: 1) the shorter the projection period, the more reliable the projection; 2) the larger the geographic area being projected the more reliable the projection; 3) the lower the current fertility and the higher the current life expectancy, the lower the projection's margin of error. Major sources of data and projections on world, regional, national, subnational, and local areas and difficulties with data for developing countries are discussed. Available microcomputer programs for IBM PC compatible machines are listed and described briefly.     

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.     

A local analysis of ethnic group population trends and projections for the UK

Projections of the UK’s ethnic populations from 2001 to 2051 show significant future change. Groups outside the White British majority will increase in size and share, not only in core areas but throughout the country. Ethnic minorities will shift out of deprived local authorities and into less deprived ones, while the White distribution remains stable. The share of the Mixed group population in the most deprived quintile (Q5) of local authorities reduces from 26 to 19%, while its share in the least deprived quintile (Q1) increases from 22 to 29%. The corresponding shifts for Asian groups are from 25 to 18% for Q5 and from 9 to 20% for the Q1. For Black groups the Q5 quintile sees a decrease from 54 to 39% while the Q1 sees an increase from 7 to 19%. There are shifts to local authorities with lower ethnic minority concentrations by Mixed, Asian and Black populations from local authorities with high ethnic concentrations, while the White, Chinese and Other group distributions remain in 2051 as they were in 2001. So, ethnic minority groups will be less segregated from the rest of the population in 2051 than in 2001. Indices of Dissimilarity between each group and the rest of the population fall by a third over the projection period. The UK in 2051 will be a more ethnically diverse society than in 2001.     

New insights into the fertility patterns of recent Polish migrants in the United Kingdom

There have been important changes in the United Kingdom’s fertility and immigration in the past decade, with a large share contributed by migrants from Poland. A detailed understanding of Polish migrant fertility is lacking, however, because the relevant data are not routinely collected. This paper provides new insights into the fertility patterns of Polish migrants in the UK, and compares these patterns with those of other large immigrant groups, the UK-born population and in Poland. We use the UK Labour Force Survey with the Own Children Method, illustrating the potential of survey data for estimating immigrant fertility in settings where other data are unavailable. We first compare the fertility patterns of recent Polish migrants with those of other key recent immigrant groups and the UK-born population; estimating Age-Specific Fertility Rates (ASFRs), and Total Fertility Rates (TFRs), by country of birth for the 2004–2012 period; the proportions in each immigrant group that arrive without children; and of those childless at arrival the proportions of women who go on to have births within a short period after arrival. Next, we compare the ASFRs and TFR for Polish migrant women with those observed in Poland. Our results show that the fertility of Polish migrants is among the lowest for all population subgroups in the UK, and that Polish migrants are less likely to have children soon after arrival than other immigrant groups. The findings are consistent with migration not being so closely linked to family formation for Polish migrants as it is for immigrants in the comparison groups. We also find that the fertility patterns of Polish migrants are different from those observed in Poland with a later childbearing profile and a slightly higher TFR.     

Projections of the ethnic minority populations of the United Kingdom 2006-2056

The ethnic minority populations in the UK are growing substantially through immigration, a youthful age structure, and in some cases relatively high fertility. Their diverse demographic and socioeconomic characteristics have attracted considerable academic and policy attention, especially insofar as those distinctive characteristics have persisted in the generations born in the UK. No official projections of the UK ethnic populations have been published since 1979. This article provides projections to 2056 and beyond of 12 ethnic groups. Given overall net immigration and vital rates as assumed in the office for National Statistics 2008-based Principal Projection, and the ethnic characteristics estimated here, the ethnic minority populations (including the Other White) would increase from 13 percent of the UK population in 2006 to 28 percent by 2031 and 44 percent by 2056, and to about half the 0-4 age group in 2056. Alternative projections assume various lower levels of immigration. Possible implications of projected changes are discussed.     

Some aspects of the use of birth expectations data from sample surveys for population projections

The value of national sample survey data relating to birth expectations for projecting births is reassessed in the light of data limitations pointed out by Ryder and Westoff among others and of the methods of projection used by the United States Bureau of the Census. The annual level of fertility under the cohort-fertility projection method depends on the assumptions regarding completed fertility, about which the available survey data are fairly informative, and on the assumptions regarding the timing of births, about which the survey data tell us very little. Test calculations suggest that Ryder and Westoff have overstated the significance of timing relative to completed family size for the level of future births. We believe that the fall in the annual total fertility rate in the first half of the sixties is to be explained only in part by a general delay in childbearing; a moderate to substantial decrease in completed family size has also occurred. Analysis of the latest set of fertility projections of the Census Bureau also suggests that the assumptions about completed fertility are a much more important determinant of the level of future births than timing, both in the short and long term. Although the available expectations data cannot help in predicting short-term annual changes in fertility, they appear useful for making long-term projections of annual fertility. Expansion of the size, frequency, and content of the sample surveys and incorporation of parity and birth interval into the projection method may improve projections.     

China’s Demographic Future Under the New Two-Child Policy

China implemented the two-child policy in 2016, however, potential impacts of this new policy on its population reality have not been adequately understood. Using population census data and 1% population sampling data during the period of 1982–2015, this study develops a fertility simulation model to explore the effects of the two-child policy on women’s total fertility rate, and employs Cohort Component Method in population projections to examine China’s demographic future with different fertility regimes. The fertility simulation results reveal that the two-child policy will make significantly positive effects on China’s total fertility rate through increasing second births, leading to a sharp but temporary increase in the first 5 years after the implementation of the new policy. In addition, population projections using simulated total fertility rates show that the Chinese population would reach its peak value around the middle 2020s and be faced with the reduction of labor force supply and rapid aging process, featured with remarkable increases in both size and share of the elderly population. The findings suggest that the two-child policy would undoubtedly affect China’s fertility rates and demographic future; however, the effects are mild and temporary.

     

A model to estimate births averted due to IUCDs and sterilizations

The computation of births averted due to a specific family planning programme requires special treatment instead of application of the usual population projection technique using conventional fertility rates. The reason for this is that adopters of a family planning method are a selective group from the general population with respect to a number of demographic and biological characteristics, including the initial susceptibility status at the time of adoption. In the present paper a matrix of annual birth probabilities specific to age at adoption of a method and duration since adoption is obtained. One matrix is presented for adopters of IUCD, another for salpingectomy, and a third for vasectomy. These matrices are used to obtain estimates of births averted for India due to IUCDs and sterilizations performed during 1956–69. The results are compared with those that could have been obtained by using the usual age-specific marital fertility rates under identical conditions, except for initial susceptibility. The entire work is programmed on a high speed electronic computer.     

The demographic assessment of family planning programs: a bibliographic essay

Over the past 15-20 years a substantial literature has accumulated in the area of determining the effect of family planning programs upon fertility, and a selected bibliography is provided. The development of modern contraceptive techniques coincided with the development of large national programs designed to reduce the fertility of the general population, and literature is presented on each of the several evaluation methods that have been used to examine program-induced changes in 1 or more fertility measures. 2 methods deal with data on individuals - births averted among acceptors and individual matching; the latter compares the fertility experience of acceptors and matched non-acceptors. A different class of methods is aggregated methods. Either areas and areal variables are the focus of the analysis proceeds with measures on general subgroups identified by such factors as residence, age, or marital status. The aggregate methods are multiple regression, program experiemnts, matching of areas, correspondence between program activity and fertility change, decomposition, and simulation. The disparity in methods has conspired with large differences in programs, data sets, and investigator interests to produce serious problems of non-comparability in results.     

Reproduction in upheaval: ethnic-specific fertility responses to societal turbulence in Kazakhstan

This study contributes to the literature on demographic adjustments to societal crises by examining ethnic-specific probabilities of having first, second, and third marital births in late-twentieth-century Kazakhstan. Discrete-time logit models, employing data from the 1995 and 1999 Kazakhstan Demographic and Health Surveys, are fitted. The results show that the probability of a first birth responded to societal cataclysms of the post-Soviet transition, but this response was most manifest and enduring in the ethnic group that had been most demographically advanced and that also found itself most politically and economically vulnerable. While ethnic differences in the probability of second and third births were generally more pronounced than in the probabilities of first birth, the pace of their post-Soviet decline was relatively uniform across all ethnic groups.     

Immigration to the UK from High‐Fertility Countries: Intergenerational Adaptation and Fertility Convergence

The fertility of immigrants' children increasingly shapes the ethnic diversity of the population in Western Europe. However, few data are available on the fertility patterns of immigrants and their offspring. This article provides new fertility estimates of immigrants and immigrants' children by ethnic group in the United Kingdom that may provide better‐informed fertility assumptions for future population projection models. The impact of migration‐specific tempo effects on the period TFR of immigrants is analyzed. Among the results, intergenerational fertility transitions strongly contribute both to fertility convergence between ethnic groups and to fertility “assimilation” or “intergenerational adaptation” to the UK mainstream childbearing behavior. Ethnic fertility convergence, particularly marked for populations originating from high‐fertility countries, reflects in part decreasing fertility in sending countries and in part intergenerational adaptation to the UK mainstream. Higher educational enrollment of the daughters of immigrants may partly explain their relatively lower fertility.     

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.     

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.     

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.     

Aboriginal population prospects

Data from the 1991 Census largely confirm earlier projections of the size and structure of the Aboriginal population, although the data for Torres Strait Islanders are markedly inconsistent with previous counts. The 1986 and 1991 Censuses mark the first intercensal period for decades for which Aboriginal population counts have been consistent. This provides an opportunity, taken in this paper, to examine closely the discrepancies between projections and the 1991 Census and to comment on ways in which determinants of Aboriginal population change are diverging from the parameters used for previous projections. We pay particular attention to mortality prospects, because of the occurrence in the 1991 Census of a higher than expected sex ratio and differences between projections and counts for certain age groups. We note the evidence for under-enumeration of the Aboriginal population in particular age groups in the 1991 Census as in previous censuses, and estimate the size of adjustments necessary to correct for some, but not all, of these deficiencies. The analysis shows that Aboriginal fertility increased in the second half of the 1980s.     

Establishing trends in atsic regional council populations using census data: A cautionary note

This paper points out that limitations in official census data for Aborigines and Torres Strait Islanders draw into question the validity of trend analysis based on time series data for Aboriginal and Torres Strait Islander Commission (ATSIC) regional council areas. Accordingly, the meaningful application of projection techniques to estimate future population profiles using existing census data is severely restricted. Among the difficulties encountered in reconstructing council area populations are census boundary changes over time, changes in enumeration techniques and coverage, the problems posed by self-identification and associated population growth, and, in some cases, the difficulty of matching ATSIC regional council boundaries with census geography. Following discussion of these problems, detailed figures showing changes in the size of the Aboriginal and Islander populations and labour force in each council area are presented using 1976 as the base year. As expected, geographic patterns of population and labour-force change are difficult to discern and exact reasons for comparative growth or decline are impossible to determine. The paper concludes that reverse projections for regional council areas using 1991 Census data would provide a more reliable basis for establishing demographic trends. Although not entirely adequate, these reconstructions for ATSIC regional councils are the only estimates of these populations that have been undertaken to date.     

Population Projections by Age for Florida and its Counties: Assessing Accuracy and the Impact of Adjustments

Projections of total population have been evaluated extensively, but few studies have investigated the performance of projections by age. Of those that did, most focused on projections for countries or other large areas. In this article, we evaluate projections by age for Florida and its counties, as produced and published between 1996 and 2010 by the Bureau of Economic and Business Research at the University of Florida. We first compare the precision and bias of projections of total population with the precision and bias of projections by age, at both the state and county levels. This is followed by a more detailed examination of county-level projection errors for individual age groups, first in the aggregate and then disaggregated by sex and population size. The second part of the analysis focuses on a number of adjustments that were implemented in projections published in 2006 and 2009. Intended to improve accuracy, these adjustments involved updates to the base population, fertility rates, and survival rates. We compare the accuracy of projections incorporating these adjustments with the accuracy of projections excluding them. We believe this study offers a unique opportunity to examine a variety of characteristics regarding the forecast accuracy of small-area population projections by age.     

Economic fortunes, ethnic divides, and marriage and fertility in Central Asia: Kazakhstan and Kyrgyzstan compared

Declining marriage and fertility rates following the collapse of state socialism have been the subject of numerous studies in Central and Eastern Europe. More recent literature has focused on marriage and fertility dynamics in the period of post-crisis political stabilization and economic growth. However, relatively little research on marriage and fertility has dealt with the Central Asian part of the post-socialist world. We use survey and published data from Kazakhstan and Kyrgyzstan, two multiethnic countries with differing paths of post-crisis recovery, to examine overall and ethnic-specific trends in entry into marriage and fertility. We find that in both countries rates of entry into marriage continued to decline throughout post-crisis years. By contrast, fertility rose, and this rise was greater in the more prosperous Kazakhstan. However, we also detect considerable ethnic variations in fertility trends which we situate within the ethnopolitical and ethnodemographic contexts of both countries.