Population forecasting theory,methods and assessments of accuracy. The magnitude of error due to different vital processes in population forecasts

The accuracy of population forecasts depends in part upon the method chosen for forecasting the vital rates of fertility, mortality, and migration. Methods for handling the stochastic propagation of error calculations in demographic forecasting are hard to do precisely. This paper discusses this obstacle in stochastic cohort-component population forecasts. The uncertainty of forecasts is due to uncertain estimates of the jump-off population and to errors in the forecasts of the vital rates. Empirically based of each source are presented and propagated through a simplified analytical model of population growth that allows assessment of the role of each component in the total error. Numerical estimates based on the errors of an actual vector ARIMA forecast of the US female population. These results broadly agree with those of the analytical model. This work especially uncertainty in the fertility forecasts to be so much higher than that in the other sources that the latter can be ignored in the propagation of error calculations for those cohorts that are born after the jump-off year of the forecast. A methodology is therefore presented which far simplifies the propagation of error calculations. It is noted, however, that the uncertainty of the jump-off population, migration, and mortality in the propagation of error for those alive at the jump-off time of the forecast must still be considered.     

Stochastic methods in population forecasting

"This paper presents a stochastic version of the demographic cohort-component method of forecasting future population. In this model the sizes of future age-sex groups are non-linear functions of random future vital rates. An approximation to their joint distribution can be obtained using linear approximations or simulation. A stochastic formulation points to the need for new empirical work on both the autocorrelations and the cross-correlations of the vital rates. Problems of forecasting declining mortality and fluctuating fertility are contrasted. A volatility measure for fertility is presented. The model can be used to calculate approximate prediction intervals for births using data from deterministic cohort-component forecasts. The paper compares the use of expert opinion in mortality forecasting with simple extrapolation techniques to see how useful each approach has been in the past. Data from the United States suggest that expert opinion may have caused systematic bias in the forecasts."     

Confidence intervals for population projections based on Monte Carlo methods

"This paper presents an approach of constructing confidence intervals by means of Monte Carlo simulation. This technique attempts to incorporate the uncertainty involved in projecting human populations by letting the fertility and net immigration rates vary as a random variable with a specific distribution. Since fertility and migration are by far the most volatile, and therefore, the most critical components to population forecasting, this technique has the potential of accounting for this uncertainty, if the subjective distributions are specified with enough care. Considering the results of the model for the U.S. in 2082, for example, it is shown that the population will number between 255 million and 355 million with a probability of 90 percent."     

Confidence intervals for population projections based on Monte Carlo methods

This paper presents an approach of constructing confidence intervals by means of Monte Carlo simulation. This technique attempts to incorporate the uncertainty involved in projecting human populations by letting the fertility and net immigration rates vary as a random variable with a specific distribution. Since fertility and migration are by far the most volatile, and therefore, the most critical components to population forecasting, this technique has the potential of accounting for this uncertainty, if the subjective distributions are specified with enough care. Considering the results of the model for the U.S. in 2082, for example, it is shown that the population will number between 255 million and 355 million with a probability of 90 percent.     

THE DEMOGRAPHIC DIVIDEND: RETROSPECT AND PROSPECT

The demographic transition, from high to low mortality and fertility, entails several decades during which a country's dependency ratio falls, bringing a demographic dividend to which a third of East Asia's late twentieth‐century economic growth ‘miracle’ has been attributed. Can a similar miracle be expected in sub‐Saharan Africa in the next few decades, or will relentless population pressure prevent this?     

Probabilistic Population Projections for India with Explicit Consideration of the Education-Fertility Link

Among the different sources of uncertainty in population forecasting, uncertain changes in the structure of heterogeneous populations have received little attention so far, although they can have significant impacts. Here we focus on the effect of changes in the educational composition of the population on the overall fertility of the population in the presence of strong fertility differentials by education. With data from India we show that alternative paths of future female enrolment in education result in significantly different total fertility rates (TFR) for the country over the coming decades, even assuming identical fertility trends within each education group. These results from multi-state population projections by education are then translated into a fully probabilistic population projection for India in which the results of alternative education scenarios are assumed to expand the uncertainty range of the future TFR in the total population.
This first attempt to endogenize structural change with respect to education—which is the greatest measurable source of fertility heterogeneity in Asia—has resulted from a larger exercise of the Asian MetaCentre for Population and Sustainable Development Analysis to collect empirical information, scientific arguments as well as informed opinions about likely future population trends in Asia from a large number of population experts in the region. In this process, future changes in the educational composition of the population have been identified as a key driver of future fertility.
The actual probabilistic population projections for India show that with high certainty, the Indian population will continue to grow to about 1.3 billion over the next quarter of a century. After that the uncertainty will get much wider, ranging from a continued strong increase to the beginning of a population decline in India.     

Migration: the trends converge

Formerly, Australia, New Zealand, Canada, and the US have served as permanent destinations for immigrants, while Europe's migrants have moved to more northerly countries to work for a time and then returned home. From 1973-1975 Europe's recruitment of foreign workers virtually ended, although family reunion for those immigrants allowed in was encouraged. Problems resulting from this new settlement migration include low paying jobs for immigrant women, high unemployment, and inadequate education for immigrant children. Illegal migrants from Latin America and the Caribbean enter the US and Canada each year while illegal North African immigrants enter Italy, Spain, and Greece. North America, Australia, and Europe have all received political refugees from Asia and Latin America. Increasingly, these foreigners compete in the labor market rather than simply fill jobs the native workers do not want. All the receiving countries have similar policy priorities: 1) more effective ways for controlling and monitoring inflows and checking illegal immigration; 2) encouraging normal living patterns and accepting refugees; and 3) integrating permanent migrants into the host country. Europe's public immigration encouragement prior to the first oil shock, has left some countries with a labor force that is reluctant to return home. It is unlikely that Europe will welcome foreign labor again in this decade, since unemployment among young people and women is high and family reunion programs may still bring in many immigrants. Less immigration pattern change will probably occur in North America, Australia, and New Zealand since these countries' populations are still growing and wages are more flexible. Immigration, regulated by policy, and emigration, determined by market forces, now are working in the same direction and will likely reduce future migration flows.     

Assessing inherent model bias: An application to native displacement in response to immigration

There is a long-standing debate among academics about the effect of immigration on native internal migration decisions. If immigrants displace natives this may indicate a direct cost of immigration in the form of decreased employment opportunity for native workers. Moreover, displacement would also imply that cross-region analyses of wage effects systematically underestimate the consequences of immigration. The widespread use of such area studies for the US and other countries makes it especially important to know whether a native internal response to immigration truly occurs. This paper introduces a microsimulation methodology to test for inherent bias in regression models that have been used in the literature. We show that some specifications have built biases into their models, thereby casting doubt on the validity of their results. We then provide a brief empirical analysis with a panel of observed US state-by-skill data. Together, our evidence argues against the existence of native displacement. This implies that cross-region analyses of immigration’s effect on wages are still informative.     

Population policy aspects of the employment of foreigners

The author considers the medium-range and long-term effects of declining fertility in the Federal Republic of Germany, including the consequences for the population, age structure, economy, and social security system. The slight rise in the number of births is attributed to the presence of foreigners, and it is suggested that only a rapid resumption of immigration will assure demographic stability (SUMMARY IN ENG)     

How do very open economies adjust to large immigration flows? Evidence from Spanish regions

We study the labor market effects of the large immigration wave in Spain between 2001 and 2006. In this period the foreign-born share increased from 6% to 13%, with a total inflow exceeding three million immigrants. Our analysis exploits the large variation in the size of immigration flows across Spain's regions. To identify causal effects, we take advantage of the fact that immigrants' location choices were strongly driven by early migrant settlements that arrived during the 1980s. We find that the relatively unskilled migration inflows did not affect the wages or employment rates of unskilled workers in the receiving regions. The growth of the unskilled labor force was absorbed mostly through increases in total employment. This increase did not originate in changes in the composition of regional output, but was instead driven by changes in skill intensity at the industry level. Regions that received a large inflow of unskilled immigrants increased the intensity of use of the now more abundant (unskilled) labor, relative to other regions. The key industries responsible for this absorption were retail, construction, hotels and restaurants and domestic services. These results are inconsistent with standard open economy models but are in line with recent empirical studies for the United States and Germany.     

Evaluating the forecast accuracy and bias of alternative population projections for states

"A common perception among producers (and users) of population projections is that complex and/or sophisticated techniques produce more accurate forecasts than simple and/or naive techniques. In this paper we test the validity of that perception by evaluating the forecast accuracy and bias of eight commonly used projection techniques drawn from...four categories [trend extrapolation, ratio extrapolation, cohort-component, and structural]. Using data for [U.S.] state population projections from a number of different time periods, we find no evidence that complex and/or sophisticated techniques produce more accurate or less biased forecasts than simple, naive techniques."     

The Effects of Immigration on Household Services,Labour Supply and Fertility

Fertility and female labour force participation are no longer negatively correlated in developed countries. At the same time, increased immigration affects supply and prices of household services, which are relevant to fertility and employment decisions. This paper analyses the effect of immigration on labour supply and fertility of native women in the UK. Adopting an instrumental variable approach, I find that immigration increases female labour supply without affecting fertility. My results show that immigration increases the size of the childcare sector, and reduces its prices, suggesting that immigrants may ease the trade‐off between working and child rearing among native women.     

THE IMPACT OF IMMIGRATION ON THE LABOR MARKET

The literature on the impact of immigration on the labor market is highly controversial. The aim of this paper is to review the existing literature and draw some general conclusions on how wages and employment respond to immigration. Economic studies indicate that the impact of immigration on the average wage and employment of native workers is null or slightly positive. However, because adjustments take time, the immediate labor market effects of unexpected (as opposed to expected) migration episodes can be detrimental. Immigration also can have distributional consequences. In particular, the skill composition of immigrants matters in determining their impact on native labor market outcomes. An inflow of immigrants will tend to reduce the wages of competing native workers (with skills similar to those of the migrants), and increase those of complementary workers (with skills that complement those of immigrants). By affecting the skill composition of the workforce, immigration can create winners and losers among native workers via changes in the wage structure.     

Immigration and firm productivity: evidence from the Canadian Employer-Employee Dynamics Database

Previous studies on the impact of immigration on productivity in developed countries remain inconclusive, and most analyses are abstracted from firms where production actually takes place. This study examines the empirical relationship between immigration and firm-level productivity in Canada. It uses the Canadian Employer-Employee Dynamics Database that tracks firms over time and matches firms with their employees. The study finds that there is a positive association between changes in the share of immigrants in a firm and changes in firm productivity. This positive effect of immigration on firm productivity is small, but it is stronger over a longer period. The effect tends to be larger for low-skilled immigrants as compared with highly-skilled workers, as firm productivity growth is more strongly associated with changes in the share of recent immigrants (relative to established immigrants), and immigrants who intended to work in non-high skilled occupations (relative to immigrants who intended to work in high-skilled occupations). Those differences are more pronounced in technology-intensive and knowledge-based industries. Immigration is found to have little estimated effects on capital intensity in a firm. Finally, this study finds that high skill and lower skill immigrants have similar effects on average worker earnings arising from the positive productivity effect of immigration, but only skilled immigrants are associated with higher firm profits.

     

Voting over selective immigration policies with immigration aversion

Selective immigration policies set lower barriers to entry for skilled workers. However, simple economic intuition suggests that skilled majorities should welcome unskilled immigrants and protect skilled natives. This paper studies the voting over a selective policy in a two-country, three-factor model with skilled and unskilled labor, endogenous migration decisions, costly border enforcement and aversion to immigration. Results show that heterogeneity in capital distribution forces skilled voters to form a coalition with unskilled voters, who become pivotal. The voting outcome is therefore biased towards the preferences of the latter, and consists in a selective protectionism. Finally, immigration aversion helps to explain why skilled majorities do not bring down entry barriers against unskilled workers.     

Toward a New Model for Probabilistic Household Forecasts

Household projections are key components of analyses of several issues of social concern, including the welfare of the elderly, housing, and environmentally significant consumption patterns. Researchers or policy makers that use such projections need appropriate representations of uncertainty in order to inform their analyses. However, the weaknesses of the traditional approach of providing alternative variants to single "best guess" projection are magnified in household projections, which have many output variables of interest, and many input variables beyond fertility, mortality, and migration. We review current methods of household projections and the potential for using them to produce probabilistic projections, which would address many of these weaknesses. We then propose a new framework for a household projection method of intermediate complexity that we believe is a good candidate for providing a basis for further development of probabilistic household projections. An extension of the traditional headship rate approach, this method is based on modelling changes in headship rates decomposed by household size as a function of variables describing demographic events such as parity specific fertility, union formation and dissolution, and leaving home. It has moderate data requirements, manageable complexity, allows for direct specification of demographic events, and produces output that includes the most important household characteristics for many applications. An illustration of how such a model might be constructed, using data on the U.S. and China over the past several decades, demonstrates the viability of the approach.     

Complements or substitutes? Task specialization by gender and nativity in Spain

Learning about the impact of immigration on the labor market outcomes of natives is a topic of major concern for immigrant-receiving countries. Using data from Spain, where the immigrant population has risen from 4% to 13% within a decade, we find that immigration appears to have affected the task specialization of natives without affecting their employment levels. However, the impact of immigration on the relative task supply of natives is twice as great in Spain as in the United States. The magnitude of the immigration impact in a country with a large share of immigrants originating from Spanish-speaking countries suggests that host country language proficiency is not the sole factor driving the observed impact. Additionally, the analysis reveals significant gender differences in the impact of immigration on the relative task supply of natives, possibly resting on the occupational concentration of immigrants and native occupational segregation patterns by gender, among other factors.     

Assumptions on Fertility in Stochastic Population Forecasts*

In recent years Statistics Netherlands has published several stochastic population forecasts. The degree of uncertainty of the future population is assessed on the basis of assumptions about the probability distribution of future fertility, mortality and migration. The assumptions on fertility are based on an analysis of historic forecasts of the total fertility rate (TFR), on time‐series models of observations of the TFR, and on expert knowledge. This latter argument‐based approach refers to the TFR distinguished by birth order. In the most recent Dutch forecast the 95% forecast interval of the total fertility rate in 2050 is assumed to range from 1.2 to 2.3 children per woman.     

Effects of Future Demographic Changes on the US Economy: Evidence from a Long-term Simulation Model

Demographics, especially the size and the age composition of the population, contribute substantially to the growth and structure of any economy. Over the next 55 years, the age composition of the US population will change dramatically, as the post-World War II ‘baby boom’ ages into retirement. In this paper, we use a long-term interindustry macro model of the US economy to examine how the age composition of the US population affects overall economic growth as well as the output/employment structure of the economy. We find that the system of funding government commitments to pension and medical care for the elderly is a primary channel through which demographic effects translate into economic effects.     

Immigrants’ Wage Growth and Selective Out‐Migration

This paper examines immigrant wage growth taking selective out‐migration into account using administrative data from the Netherlands. Addressing a limitation in the previous literature, we address the potential endogeneity of immigrants’ labour supply and out‐migration decisions on their earning profiles using a correlated competing risk model. We distinguish between labour and family migrants, given their different labour market and out‐migration behaviours. Our findings show that accounting for selective labour supply is as important as accounting for selective out‐migration. Controlling only for out‐migration selectivity would underestimate immigrants’ wage growth, whilst controlling only for labour market selectivity would overestimate their wage growth. This shows that different selections are important for different types of migrants.