Modelling international migration to produce local level estimates
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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

Modelling international migration to produce local level estimates

Ruth Fulton

Office for National Statistics


Outline of presentation

Outline of presentation

Context

Immigration

  • Current method

  • Using administrative data

  • Modelling approach

    Data sources, Fitting the model,

    Diagnostics/ validation, Impact on estimates

    Emigration


Context of work

Context of work

  • Improving Migration and Population Statistics (IMPS)

  • Previous improvements to immigration and emigration methodology (2007)

  • Forthcoming package of improvements

    (May 2010)


The importance of international migration

The importance of international migration

  • Key driver of population change


Current method immigration

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


Current method issue

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


Improving the current method

Improving the current method:


Use of administrative data

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


Comparison of flag 4s and ninos

Comparison of Flag 4s and NINos


A modelling approach

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


Model specification

Model specification

where

= direct IPS estimate, no. immigrants going to LADj

= expected total count of immigrants, LADj

= set of covariates for LADj


Alternative approaches

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


Variables entered for potential selection

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


Fixed covariates currently in the model

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


Diagnostic and validation tests

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


Time series check

Time series check


Model vs sample estimate plot 04 05

Model vs Sample Estimate plot (04/05)


04 05

04/05

Existing

New


Preliminary impacts assessment

Preliminary Impacts Assessment


Current methods emigration

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)


  • Improvements

    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


    Impact of model based distribution

    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


    Further information

    Further Information

    • Quarterly updates and other information at www.statistics.gov.uk/imps

    • Email:

      • [email protected]

      • [email protected]

    • Consultation papers (December 09)


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