A model-based approach for estimating international emigration forlocal authorities

Brian Foley, Office for National Statistics

BSPS day meetingLondon School of Economics

16th May 2013

Presentation format

• Background information- importance of accurate international migration

estimates

• Issues with estimating emigration from local authorities (LAs)

• ONS emigration model- overview- updating of the model for the year ending mid-

2012 emigration estimates

• Future work

Need for accurate international migration estimates at local authority level

• International migration is a key component of population change

• Accurate estimation of migration flows necessary for LA mid-year population estimates

Definition

• ONS use the United Nations recommended definition of an international long-term migrant:- a person who moves to a country other than that

of his or her usual residence for a period of at least a year (12 months), so that the country of destination effectively becomes his or her new country of usual residence

Estimating international migration at local authority level

• Migration Statistics Improvement Programme• Administrative data to distribute immigration

totals from International Passenger Survey (IPS) - National Insurance number- Higher Education Statistics Agency- Flag 4s from the GP Patient Register

• What about emigration ??

Emigration at local authority level – difficult to estimate

• No administrative or survey data sources exist that provide information on long-term emigration from LAs

• Small sample size of emigrants in the IPS

International Passenger Survey, 2002 to 2011

Source - http://www.ons.gov.uk/ons/rel/migration1/long-term-international-migration/2011/1-02-ips-margins-of-error--1975-2011.xls

IPS estimates of emigration at national (2002-2011) and regional level (2011)

Source - http://www.ons.gov.uk/ons/rel/migration1/long-term-international-migration/2011/1-02-ips-margins-of-error--1975-2011.xls

Emigration estimates for the different levels of geography

IPS direct estimate

IPS direct estimate

Distribute using IPS 3 year average

Distribute using regression model

National

Regional

Intermediate(NMGo)

Local authority

Estimating emigration at local authority level

• ONS employs a Poisson regression model• Produces estimates of international

emigration at LA level (where IPS data are insufficient) by borrowing strength from other data sources- Census- Survey- Administrative

Overview of the emigration model

• Fitted model based on relationship between number of emigrants leaving an LA (IPS-based) and a number of LA-level socio-economic and demographic variables (covariates)

• Strengths of model:- availability of data for all LAs- more robust estimates

Consideration of covariate data

• Variety of factors associated with why emigrants would leave an area

• Data that capture both a person’s desire and ability to emigrate

Relationship between international long-term emigration and socio-demographic variables at local authority level in England and Wales, year ending mid-2011

Stepwise model

IPS estimate of LA emigration

(3 year average)

Covariate 1

Covariate 2

Covariate i

Covariate 3

Covariate 1

Multicollinearity testing

Covariates selected by stepwise model in more than one year

LA level data

Emigration model specification

Covariate i

Final modelLA emigration estimates constrained to sum to the relevant NMGo estimate

Fitting the final model

• Geographic indicators included• Model fitted for each year ending mid-2002 to

mid-2006 • Fixed set of model covariates used

- improves quality of time series

• General patterns can be observed- relationship between covariates and IPS

emigration estimates

Original emigration model (finalised 2010)

LA emigration estimates

Number of retired people (-)

Number of lone and working parents (-)

Number of students in Higher/Further education (+)

Number of people of Western Europe country of birth (+)

Number of people of Oceania country of birth (+)

Number of people of North American country of birth (+)

Number of household spaces in terraced housing (+)

Number of household spaces in shared housing (+)

Number of hostels (+)

Number of people of Indian ethnicity (-)

Number of internal in-migrants (-)

Number of international in-migrants (+)

Annual Population Survey

2001 Census

Population Statistics Division, ONS

Updating the model for the year ending mid-2012 emigration estimates

• Rationale- availability of 2011 Census data- availability of administrative data- appropriate to re-examine the underlying relationships

in the model over a more recent time-period- change in dynamics of international migration to/from

UK since the mid-2000s

Covariate data sources employed

• 2011 Census data- country of birth, ethnicity, housing status

• Administrative data available to ONS- Higher Education Statistics Agency (HESA)- Migrant Worker Scan

• Annual Population Survey- economic activity data

• Home Office - crime statistics

Stepwise model

IPS estimate of LA emigration

(3 year average)

Covariate 1

Covariate 2

Covariate i

Covariate 3

Covariate 1

Multicollinearity testing

Covariates selected by stepwise model in more than one year

LA level data

Emigration model specification

Covariate i

Final modelLA emigration estimates constrained to sum to the relevant NMGo estimate

Updated model for year ending mid-2012 emigration estimates at LA level

Number of hostels (+)

Number of people of Oceania country of birth (+)

Number of people of African country of birth (+)

Number of people aged 16+ in employment (-)

Number of people of North American country of birth (+)

Number of in-migrants of EU8 nationality (+)

LA emigration estimates

Annual Population Survey

2011 Census

Migrant Worker Scan

• Range from ca. 20 to 8,000

• Higher emigration flows associated with London and the larger regional cities

<250250-499500-749750-9991,000-1,9992,000-3,9994,000-6,999>7,000

Modelled estimates of emigration from local authorities in England and Wales, year ending mid-2011

Modelled emigration estimates

• Range from ca. 0.2% to 6.0%

• Modelled emigration estimates less than 2% of the LA population in 340 of the 348 LAs in England and Wales

<0.200.20-0.340.35-0.490.50-0.740.75-0.991.00-1.491.50-2.49>2.50

Modelled estimates of emigration as a percentage of local authority population, year ending mid-2011

Emigration as % of LA population

Future work

• Ongoing research into developing an improved modelling approach for producing emigration estimates at LA level- identify additional covariates, other data sources- capture forthcoming changes in international

migration patterns to/from UK- reassess how geographic effects are captured and

accounted for

Thank you for your attention

Any questions ?