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Modelling international migration to produce local level estimates

Modelling international migration to produce local level estimates. Ruth Fulton Office for National Statistics. Outline of presentation. Context Immigration Current method Using administrative data Modelling approach Data sources, Fitting the model,

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Modelling international migration to produce local level estimates

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  1. Modelling international migration to produce local level estimates Ruth Fulton Office for National Statistics

  2. Outline of presentation Context Immigration • Current method • Using administrative data • Modelling approach Data sources, Fitting the model, Diagnostics/ validation, Impact on estimates Emigration

  3. Context of work • Improving Migration and Population Statistics (IMPS) • Previous improvements to immigration and emigration methodology (2007) • Forthcoming package of improvements (May 2010)

  4. The importance of international migration • Key driver of population change

  5. Current method: immigration • National level • International Passenger Survey (IPS) data only • Government Office Region (GOR) & Wales level • IPS data calibrated to Labour Force Survey (LFS) data • LFS data averaged over three years • Intermediate geography level • IPS data averaged over three years • Local authority level • 2001 Census data

  6. Current method: issue • Current method uses 2001 Census data to distribute to LA level • Clear changes in migration trends since 2001 • e.g. EU accession • Bias introduced to LA estimates where Census distribution has changed

  7. Improving the current method:

  8. Use of administrative data • Potential use of administrative data: • GP registrations (Flag 4s) • National Insurance Number (NINo) allocations to overseas nationals • Improves timeliness at LA level • Differences in coverage and definitions

  9. Comparison of Flag 4s and NINos

  10. A modelling approach • Produces estimates for LAs (IPS data cannot be used directly at this level) • ‘Borrows strength’ from other data sources (covariates) • Model fitted at the LA level describing relationship between IPS and covariates • Fitted model can be used to obtain LA estimates

  11. Model specification where = direct IPS estimate, no. immigrants going to LADj = expected total count of immigrants, LADj = set of covariates for LADj

  12. Alternative approaches • Modelling IPS sample counts • Modelling IPS sample counts, with average LA weight as offset OR additional covariate • Scaling IPS direct estimate to a count scale (or standardising IPS sample count) • Fitting model at NMGi level, estimating coefficients and applying model at LA level

  13. Variables entered for potential selection Industry Job Centre Vacancies Foreign Armed Forces Home Armed Forces Mid-year Pop Est UK-born Immigrants Ethnic Population Population Density Flag 4s Internal Migration Country of Birth Unemp Estimates NINos Foreign Students

  14. Fixed covariates currently in the model Job Centre Vacancies Mid-year Pop Est UK-born Immigrants Ethnic Population Population Density Flag 4s Internal Migration Country of Birth Foreign Armed Forces Unemp Estimates Home Armed Forces NINoS Foreign Students Industry

  15. Diagnostic and Validation tests • Model diagnostics • Pseudo R2 • Residual plots • Model vs Sample estimate plots • Comparing the 2001 model based estimates with the 2001 Census data • Comparing the sum of the model based estimates for LAs with the NMGi estimate • Checking the time-series

  16. Time series check

  17. Model vs Sample Estimate plot (04/05)

  18. 04/05 Existing New

  19. Preliminary Impacts Assessment

  20. Current methods: emigration • National level • International Passenger Survey (IPS) data only • Government Office Region (GOR) & Wales level • IPS data only • Intermediate geography level • IPS data averaged over three years • Local authority level • Model based distribution (propensity to migrate)

  21. Improvements • Fits model at local authority level rather than intermediate geography level • Uses Poisson modelling and models number of migrants rather than propensity to migrate • Tested some additional covariates, e.g. more detailed ethnic group and fixes covariates

  22. Impact of model based distribution • Only affects the distribution of number of immigrants and emigrants within the intermediate geography • Migration estimates for local authorities will change for mid-2002 to mid-2008 as a result

  23. Further Information • Quarterly updates and other information at www.statistics.gov.uk/imps • Email: • imps@ons.gsi.gov.uk • ruth.fulton@ons.gov.uk • Consultation papers (December 09)

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