The Estimation of Place-to-Place Migration Flows Using an Alternative Log-Linear Parameter Coding Scheme

The log-linear model, with an alternative parameter coding scheme, is used in this paper to obtain estimates of place-to-place migration flows in situations where the data are inadequate or missing. The alternative parameter coding scheme is particularly useful in constructing the origin-destination interaction structure. To illustrate the method, two empirical examples are presented. The first demonstrates the effectiveness of the methodology by estimating known migration flows between states in the Western region of the United States during the 1985-1990 period. The second example focuses on estimating international migration flows in the Northern region of Europe during the 1999-2000 period where the data are incomplete. Both examples demonstrate the usefulness and generality of this particular method for estimating migration flows

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

There have been important changes in the United Kingdom’s (UK) 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 with patterns in Poland. We use the UK Labour Force Survey with the Own Child(ren) 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: 1) Age-Specific Fertility Rates (ASFRs), and Total Fertility Rates (TFRs), by country of birth for the 2004-2012 period, 2) The proportions in each immigrant group that arrive without children, and, 3) Of those childless at arrival the proportions of women who go on to have births within a short period of 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 amongst 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 to those observed in Poland with a later childbearing profile and a slightly higher TFR

Does specification matter? Experiments with simple multiregional probabilistic population projections

Population projection models that introduce uncertainty are a growing subset of projection models in general. In this paper, we focus on the importance of decisions made with regard to the model specifications adopted. We compare the forecasts and prediction intervals associated with four simple regional population projection models: a total growth rate model, a component model with net migration, a component model with in-migration and outmigration rates, and a multiregional model with destination-specific out-migration rates. Vector autoregressive models are used to forecast future rates of growth, birth, death, net migration, in-migration and out-migration, and destination-specific out-migration for the North, Midlands and South regions in England (additional specification decisions once again come into play). They are also used to forecast different international migration measures. The base data represent a time series of annual data provided by the Office for National Statistics from 1976 to 2008. The results illustrate how both the forecasted subpopulation totals and the corresponding prediction intervals differ for the multiregional model in comparison to other simpler models, as well as for different assumptions about international migration. The paper ends end with a discussion of our results and possible directions for future researc

White and Non-White Migration between Area Groups in England and Wales

In this paper, we explore internal migration in England and Wales by broad groups of ethnicity, education and employment status from 1991 to 2004. The aim is to identify key differences in the patterns and trends over time so that a better understanding of the processes can take place. Our analyses focus on migration between twelve area groups defined by the Office for National Statistics, which are comprised of Local Authority Districts and include such areas as London Cosmopolitan, London Suburbs, Coastal and Countryside and Industrial Hinterlands. By analysing the migration flows between these area groupings, we can focus our attention on the types of destinations various migrant groups choose given particular origin types. The data come from the 2001 Census and the National Health Service Central Register from 1991 to 2004. Strong stability over time is demonstrated in the aggregate patterns of origin-destination-specific flows. However, when disaggregated by region, ethnicity, education and employment, very different patterns emerge which gives some useful insights into the redistribution of England and Wales' ethnic populations and compositions

Putting the pieces of the puzzle together: Age and sex-specific estimates of migration amongst countries in the EU/EFTA, 2002-2007

Because of inconsistencies in reported flows and large amounts of missing data, our knowledge of international migration patterns in Europe is limited. Methods for overcoming data obstacles and harmonising international migration data, however, are improving. In this paper, we provide a methodology for integrating various pieces of incomplete information together, including a partial set of harmonised migration flows, to estimate a complete set of migration flows by origin, destination, age and sex for the 31 countries in the European Union and European Free Trade Association from 2002 to 2007. The results represent a synthetic data base that can be used to inform population projections, policy decisions and migration theory.Du fait d’incohérences dans l’enregistrement des flux migratoires et du grand nombre de données manquantes, notre connaissance des schémas de migrations internationales en Europe reste limitée. Cependant, les méthodes disponibles pour surmonter les obstacles liés aux données et pour harmoniser les données sur la migration internationale s’améliorent. Dans cet article, nous proposons une méthode pour combiner les différents éléments de ces informations incomplètes, incluant un ensemble partiel de données harmonisées sur les flux migratoires, afin d’estimer une série complète de flux migratoires par pays d’origine, pays de destination, âge et sexe pour les 31 pays de l’Union Européenne et de l’Association Européenne de Libre Echange de 2002 à 2007. Les résultats constituent une base de données synthétique pouvant servir de base pour les projections de population, les décisions politiques et les théories relatives à la migration

Improving estimates of migration flows to Eurostat

In this paper we identify the current mandatory requirements and issues concerning the supply of detailed migration data to Eurostat. Using simple illustrations on immigration to the United Kingdom, we show how substantial and significant improvements can be made to the flows reported by the International Passenger Survey, which contain irregularities and missing data due to its relatively small sample size. Our general methodology is based on the idea of smoothing, repairing and combining data within multiplicative component framework

What do Bayesian methods offer population forecasters?

The Bayesian approach has a number of attractive properties for probabilistic forecasting. In this paper, we apply Bayesian time series models to obtain future population estimates with uncertainty for England and Wales. To account for heterogeneity found in the historical data, we add parameters to represent the stochastic volatility in the error terms. Uncertainty in model choice is incorporated through Bayesian model averaging techniques. The resulting predictive distributions from Bayesian forecasting models have two main advantages over those obtained using traditional stochastic models. Firstly, data and uncertainties in the parameters and model choice are explicitly included using probability distributions. As a result, more realistic probabilistic population forecasts can be obtained. Second, Bayesian models formally allow the incorporation of expert opinion, including uncertainty, into the forecast. Our results are discussed in relation to classical time series methods and existing cohort component projections. This paper demonstrates the flexibility of the Bayesian approach to simple population forecasting and provides insights into further developments of more complicated population models that include, for example, components of demographic change

Integrated Modelling of European Migration: Background, specification and results

The aims of this paper are to present the background and specification of the Integrated Modelling of European Migration (IMEM) model. Currently, international migration data are collected by individual countries with separate collection systems and designs. This creates problems when attempting to understand or predict population movements between countries as the reported data are inconsistent in terms of their availability, definitions and quality. Rather than wait for countries to harmonise their migration data collection and reporting systems, we propose a model to overcome the limitations of the various data sources. In particular, we propose a Bayesian model for harmonising and correcting the inadequacies in the available data and for estimating the completely missing flows. The focus is on estimating recent international migration flows amongst countries in the European Union (EU) and European Free Trade Association (EFTA) from 2002 to 2008, using data collected by Eurostat and other national and international institutions. We also include additional information provided by experts on the effects of undercount, measurement and accuracy. The methodology is integrated and capable of providing a synthetic data base with measures of uncertainty for international migration flows and other model parameters.

High Density Genetic Maps of Seashore Paspalum Using Genotyping-By-Sequencing and Their Relationship to The Sorghum Bicolor Genome.

As a step towards trait mapping in the halophyte seashore paspalum (Paspalum vaginatum Sw.), we developed an F1 mapping population from a cross between two genetically diverse and heterozygous accessions, 509022 and HI33. Progeny were genotyped using a genotyping-by-sequencing (GBS) approach and sequence reads were analyzed for single nucleotide polymorphisms (SNPs) using the UGbS-Flex pipeline. More markers were identified that segregated in the maternal parent (HA maps) compared to the paternal parent (AH maps), suggesting that 509022 had overall higher levels of heterozygosity than HI33. We also generated maps that consisted of markers that were heterozygous in both parents (HH maps). The AH, HA and HH maps each comprised more than 1000 markers. Markers formed 10 linkage groups, corresponding to the ten seashore paspalum chromosomes. Comparative analyses showed that each seashore paspalum chromosome was syntenic to and highly colinear with a single sorghum chromosome. Four inversions were identified, two of which were sorghum-specific while the other two were likely specific to seashore paspalum. These high-density maps are the first available genetic maps for seashore paspalum. The maps will provide a valuable tool for plant breeders and others in the Paspalum community to identify traits of interest, including salt tolerance