Can We Rely on Projections of the Immigrant Population? The Case of Norway

Demographic forecasters must be realistic about how well they can predict future populations, and it is important that they include estimates of uncertainty in their forecasts. Here we focus on the future development of the immigrant population of Norway and their Norwegian-born children ("second generation"), grouped by three categories of country background: 1. West European countries plus the United States, Canada, Australia, and New Zealand; 2. Central and East European countries that are members of the European Union; 3. other countries. We show how to use a probabilistic forecast to assess the reliability of projections of the immigrant population and their children. We employ the method of random shares using data for immigrants and their children for 2000-2021. We model their age- and sex-specific shares relative to the whole population. Relational models are used for the age patterns in these shares, and time series models to extrapolate the parameters of the age patterns. We compute a probabilistic forecast for six population sub-groups with immigration background, and one for non-immigrants. The probabilistic forecast is calibrated against Statistics Norway's official population projection. We find that a few population trends are quite certain: strong increases to 2060 in the size of the immigrant population (more specifically those who belong to country group 3) and of Norwegian-born children of immigrants. However, prediction intervals around the forecasts of immigrants and their children by one-year age groups are so wide that these forecasts are not reliable.

Do Japanese and Italian Women Live Longer than Women in Scandinavia?

Life expectancies at birth are routinely computed from period life tables. When mortality is falling, such period life expectancies will typically underestimate real life expectancies, that is, life expectancies for birth cohorts. Hence, it becomes problematic to compare period life expectancies between countries when they have different historical mortality developments. For instance, life expectancies for countries in which the longevity improved early (like Norway and Sweden) are difficult to compare with those in countries where it improved later (like Italy and Japan). To get a fair comparison between the countries, one should consider cohort data. Since cohort life expectancies can only be computed for cohorts that were born more than a hundred years ago, in this paper we suggest that for younger cohorts one may consider the expected number of years lost up to a given age. Contrary to the results based on period data, our cohort results then indicate that Italian women may expect to lose more years than women in Norway and Sweden, while there are no indications that Japanese women will lose fewer years than women in Scandinavia. The large differences seen for period data may just be an artefact due to the distortion that period life tables imply in times of changing mortality.

Simulating the life course of psoriasis patients: the interplay between therapy intervention and marital status

BACKGROUND

Psoriasis, a chronic relapsing inflammatory disease affecting primarily the skin, shows multiple comorbidities including depression, cardiovascular diseases and other relevant conditions. Psoriasis patients experience social isolation, job loss, financial difficulties and partnership problems. Inversely, psychosocial impairments may negatively influence the disease course.

OBJECTIVE

To explore the feasibility of a model describing the interaction of psychosocial and clinical factors over the life course of patients.

METHODS

We considered only seven states for members of a hypothetical population: single and healthy, single and having a psoriasis flare, single and 'cured', coupled and healthy, coupled and having a psoriasis flare, coupled and 'cured', and dead. Transition probabilities between states were taken from the Norwegian Population Register for the healthy population and from epidemiological research articles. Clinical experience allowed adjustments on the assumed parameters.

RESULTS

Our macromodel, which simulates the effect of therapy intervention on patients' partnership status, yields a description of the transitions between the seven states. Treatment efficacy shows only a negligible effect on the chances of living with a partner.

CONCLUSIONS

Mathematical modelling of interactions between social and health variables is in principle feasible. However, complex models, comprising more variables (for instance: employment status, depression level, obesity etc.), are needed for more realistic simulations for the interactions studied. As increasing the number of variables leads to an exponential increase of the model's state space, switching to micromodelling (representing each individual separately) may be necessary.

Predictive intervals for age-specific fertility

A multivariate ARIMA model is combined with a Gamma curve to predict confidence intervals for age-specific birth rates by 1-year age groups. The method is applied to observed age-specific births in Norway between 1900 and 1995, and predictive intervals are computed for each year up to 2050. The predicted two-thirds confidence intervals for Total Fertility (TF) around 2010 agree well with TF errors in old population forecasts made by Statistics Norway. The method gives useful predictions for age-specific fertility up to the years 2020-30. For later years, the intervals become too wide. Methods that do not take into account estimation errors in the ARIMA model coefficients underestimate the uncertainty for future TF values. The findings suggest that the margin between high and low fertility variants in official population forecasts for many Western countries are too narrow.

Adjustments of public pension schemes in twelve industrialized countries: possible answers to population ageing

"This article analyses the impact of population dynamics on future public pension expenditure in twelve industrialized countries. Whereas previous studies have mainly emphasized ageing effects, this study looks into the consequences of changing marital status structures as well. Old age pensions, disability, and survivor's pensions are investigated. Various sets of demographic and pension scenarios are formulated for the projections, dealing with changes in demographic, labour force and pension system variables in the future. The analyses show that there can be no adequate demographic response to rising pension costs caused by population ageing at the horizon 2030. Neither an increase in fertility nor an inflow of migrants can rejuvenate national populations, unless fertility and/or migration reach unrealistically high levels. Instead, substantial reductions of the public pension burden have to be sought in socioeconomic measures." (SUMMARY IN FRE)

Sensitivity analysis in a multidimensional demographic projection model with a two-sex algorithm

"Formulas are derived for the effect that a slight change in the occurrence/exposure rate of the multidimensional projection model has on the elements of the population vector. The projection model classifies the population by sex, age, and marital status. The model includes a two-sex algorithm in order to ensure consistency between numbers of male and female marriages, number of divorces for the two sexes, and new widows (widowers) and deceased spouses. The sensitivity functions and elasticities are applied to data from the Netherlands for the period 1980-1984. The results indicate that marriage market mechanisms, in particular competition and substitution effects, are reasonably well modelled."

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."

National population forecasts in industrialized countries: main findings of an international workshop

The main findings are presented from a workshop on national population projections in developed countries, held in Voorburg, Netherlands, October 25-28, 1988. "The programme concentrated on four themes: general aspects of national population projections, fertility, mortality and international migration. Under the first theme, an international comparison of the forecasting process was presented, and items like accuracy, variants and monitoring were discussed. The other sessions contained cross-country overviews of actual trends, most recent assumptions and currently applied extrapolation methods. Furthermore, special attention was given to the use of time series methods and explanatory models for the extrapolation of fertility."

Recent trends in family and household composition in europe

"This article attempts to give a broad overview of trends in family and household composition in Europe during the last few decades. The focus is on Western Europe. We look at the decreasing average size of the household and the family (section 2) and its demographic causes. The changing role of the traditional family is reviewed in section 3, while section 4 contains a discussion of non-traditional household types: one-parent families, consensual unions and one-person households. Future trends in living arrangements are explored in section 5, where simulation results of a dynamic household model, applied to the Netherlands, are presented." (SUMMARY IN FRE)

Nuptiality models and the two-sex problem in national population forecasts

"This paper describes the two-sex problem in nuptiality models, focussing on applications in national population forecasts. Requirements for a realistic two-sex marriage model are mentioned, together with additional considerations important in the context of official forecasts. Recent nuptiality models violate the requirements to a certain extent and/or do not meet the additional considerations. A new model, used in the 1980-based population forecasts of the Netherlands compiled by the Netherlands' Central Bureau of Statistics, is described." (summary in FRE)