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James Raymer with Peter W.F. Smith and Corrado Giulietti

Combining migration data from multiple sources: Applications to internal movements in England, 1999-2007. James Raymer with Peter W.F. Smith and Corrado Giulietti Southampton Statistical Sciences Research Insitute (S3RI).

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James Raymer with Peter W.F. Smith and Corrado Giulietti

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  1. Combining migration data from multiple sources: Applications to internal movements in England, 1999-2007 James Raymer with Peter W.F. Smith and Corrado Giulietti Southampton Statistical Sciences Research Insitute (S3RI) Centre for Spatial Analysis and Policy, University of Leeds, 19 February 2009

  2. ESRC project on Combining Migration Data in England and Wales • Develop a methodology for combining migration data and for producing ‘more detailed’ flows over time • Applications include flows by ethnicity, economic activity and education at regional, county and area group levels

  3. Background • Internal migration data in England are limited due to differences in sources, availability, quality and measurement, e.g., • National Health Service Central Register • Census • Labour Force Survey

  4. Significance • The combination of multiple data sources increases the capacity to study migration and population change for specific groups by producing • harmonised data sets • time series • Estimates can be used for subnational projections, planning or policies

  5. Outline • A general log-linear model for combining data • Ethnic migration at regional level, 1991-2007 • Combining census and health registration data • Results • Economic activity migration at county level, 1999-2007 • Combining census, survey and health registration data • Results • Conclusions and future work

  6. A general log-linear model for combining migration data • We are interested in estimating five-way migration flow tables over time • The five dimensions are origin, destination, age, sex and some other ‘more detailed’ variable • Migration flow tables are composed of various hierarchical structures, not all of which are necessary for accurate prediction • If certain (important) structures are unavailable, they can be ‘borrowed’ from auxiliary data sources

  7. Log-linear models for origin, destination and age migration flow tables • Saturated model • Unsaturated model • Unsaturated-with-offset model

  8. Ethnic migration • Categorical variables • 9 origins (O) and destinations (D) • 16 age groups (A) • 2 sexes (S) • 4 ethnic groups (E) • 1991-2007 National Health Service (NHS) register* • OD, OAS and DAS tables each year • 1991 and 2001 censuses • ODAS and ODSE * Males undercounted

  9. Reported proportions of NHS interregional migration in England by sex, 1991-2007 1991 and 2001 Census = 50.8 M and 49.2 F

  10. Age patterns of NHS interregional migration in England by sex, 1991 and 2007

  11. Adjustment ratios for NHS migration data

  12. Basic framework • Data preparation • Identification of key structures and theoretical model • Estimate the flows • Analyse the results

  13. Identifying the ethnic migration model: Analysis of Census 2001 data structures • ODAS table • Key structures are OD, OA, DA and AS • ODSE table • Key structures are ODE, S • Theoretical model (ODASE) • ODE, OA, DA, AS

  14. NHSCR Census Model specification • Steps • Construct time series of ODE tables using geometric interpolation of counts from 1992 to 2000 and extrapolation to 2007 • Use iterative proportional fitting to estimate flows, where the ODE tables are adjusted to match simultaneously all of the counts imposed by the NHSCR tables • Adjust counts of males for three age groups

  15. Results: Estimated levels of South Asian, Black and Chinese & Other interregional migration in England, 1991-2007 % White 1991 = 94 2001 = 90 2007 = 85

  16. White South Asian SE SE Results: Estimated interregional migration from London by ethnicity, 1991-2007 EA EA WM SW Black Chinese & Other SE EA SE EA WM

  17. White South Asian Results: Estimated interregional migration from South East by ethnicity, 1991-2007 LO LO SW EA Black Chinese & Other LO LO

  18. Results: Estimated age-specific migration of female South Asians: 1991, 1999 and 2007 West Midlands to London South East to London London to South East London to West Midlands

  19. Categorical variables • 47 origins (O) and destinations (D) • 12 age groups, 15-74 (A) • 2 sexes (S) • 6 economic activity groups (G): Self employed, employee, unemployed, retired, other inactive and students • 1999-2007 NHS Patient Registry Data System* • OD, OAS and DAS tables each year • 2001 census • ODAS and ODSG • 1999-2007 Labour Force Survey • AG and SG Economic activity migration * Males undercounted

  20. Age patterns of PRDS inter-county migration in England by sex, 1999 and 2007

  21. Identifying the economic activity migration model • Theoretical model (ODASG) • ODG, OA, DA, AS, AG, SG • 1st step: Combine LFS and Census data • 2nd step: Combine estimates from 1st step with PRDS data

  22. Results: Overall levels of migration by economic activity groups, 1999-2007

  23. Results: Spatial patterns of employee and inactive migration from Greater Manchester (top 10 flows), 1999 Employee Inactive

  24. Results: Spatial patterns of student migration from Greater Manchester and Hampshire (top 10 flows), 1999

  25. Results: Spatial patterns of retired migration from Greater Manchester and Hampshire (top 10 flows), 1999

  26. Results: Spatial patterns of retired migration from Greater Manchester (top 5 flows), 1999-2007

  27. Results: Age- and sex-specific migration of selected economic activity groups from Greater Manchester (top flow), 1999 Retired to Lancashire Employee to Cheshire Students to West Yorkshire Inactive to Lancashire

  28. Conclusions • Flexible model and framework for combining migration data • Level of detail • Geography • Sources of information • Result is a synthetic data base that takes advantage of several available data sources • Estimates can be used for analysis, projections or planning

  29. Future work • In the next six months • Model ethnic migration flows at county level • Extend approach to estimate flows by education • Test model to predict flows between local authorities, say, within a county or region • In the next few years… • Link this framework and resulting estimates with subnational population modelling • Extend this framework to analyse other transition data, such as health, labour force and household change

  30. Contact information James Raymer Southampton Statistical Sciences Research Institute (S3RI) University of Southampton Southampton SO17 1BJ Email: raymer@soton.ac.uk See also Raymer J, Smith PWF and Giulietti C (2008) Combining census and registration data to analyse ethnic migration patterns in England from 1991 to 2007. University of Southampton Statistical Sciences Institute Methodological Working Paper, M08/09. Available at: http://eprints.soton.ac.uk/63739/01/s3ri-workingpaper-M08-09.pdf

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