47,403 research outputs found
Describing and projecting the age and spatial structures of interregional migration in Italy
No full textA multiplicative component model is applied in this paper to present a simple, yet powerful, framework for analyzing and projecting internal migration flows. The multiplicative components are useful for identifying important underlying structures in the migration patterns. To demonstrate, seven periods of age-specific interregional migration in Italy (1970-1971 to 2000-2001) are analyzed. This information is then used to project the age and spatial structures forward to the 2010-2011 period. The projection model focuses on the underlying structures, which allows both the stable and changing aspects of the migration patterns to be included
The American Community Survey's Interstate Migration Data: Strategies for Smoothing Irregular Age Patterns
No full textAge- and origin-destination-specific flows obtained from population samples often contain irregularities. The reason for this has mostly to do with the fact that migrations are relatively rare events. Biases in the analysis of migration flows can arise if these irregularities are not corrected for. Furthermore, accurate migration data are needed to understand population change and migration behavior. In this paper, we illustrate some typical examples of age-specific migration flows with irregular patterns, using the 2000-2005 American Community Survey (ACS) data. We then demonstrate how model migration schedules, log-linear models or a combination of both can be used to smooth the irregularities
The Estimation of Place-to-Place Migration Flows Using an Alternative Log-Linear Parameter Coding Scheme
No full textThe 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
Using Age and Spatial Flow Structures in the Indirect Estimation of Migration Streams
No full textThis paper presents a modeling strategy for describing and estimating interregional migration flows. The categorical log-linear model is used to demonstrate various approaches to estimation, including direct and indirect methods. And estimates of known data on interdivisional migration patterns in the United States during the 1995-2000 period are used to illustrate the effectiveness of the various log-linear models. The important aspects of the modeling strategy presented in this paper include parameter interpretation, incorporation of auxiliary or a priori information, and assessment of the various model predictions. The results show that capturing the interactions between origins and destinations are very important for accurate predictions
Improving estimates of migration flows to Eurostat
No full textIn 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
Putting the pieces of the puzzle together: Age and sex-specific estimates of migration amongst countries in the EU/EFTA, 2002-2007
No full textBecause 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
White and Non-White Migration between Area Groups in England and Wales
No full textIn 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
Unimpaired phase-sensitive amplification by vector four-wave mixing near the zero-dispersion frequency
No full textPhase-sensitive amplification (PSA), which is produced by degenerate four-wave mixing (FWM) in a randomly-birefringent fiber, has the potential to improve the performance of optical communication systems. Scalar FWM, which is driven by parallel pumps, is impaired by the generation of pump-pump and pump-signal harmonics, which limit the level, and modify the phase sensitivity, of the signal gain. In contrast, vector FWM, which is driven by perpendicular pumps, is not impaired by the generation of harmonics. Vector FWM produces PSA with the classical properties of a one-mode squeezing transformation. © 2007 Optical Society of America
New insights into the fertility patterns of recent Polish migrants in the United Kingdom
No full textThere 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
What do Bayesian methods offer population forecasters?
No full textThe 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
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