Transcript A model-based approach for estimating international emigration for local authorities Brian Foley, Office for National Statistics BSPS day meeting London School of Economics 16th May 2013

A model-based approach for
estimating international emigration for
local authorities
Brian Foley, Office for National Statistics
BSPS day meeting
London 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 mid2012 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/longterm-international-migration/2011/1-02-ips-margins-oferror--1975-2011.xls
Emigration estimates for the different
levels of geography
National
IPS direct estimate
Regional
IPS direct estimate
Intermediate
(NMGo)
Local authority
Distribute using IPS 3
year average
Distribute using
regression model
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 (IPSbased) and a number of LA-level socioeconomic 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
Emigration model specification
LA level data
IPS estimate of
LA emigration
(3 year average)
Covariate i
Covariate 1
Covariate 2
Covariate 3
Covariate 1
Stepwise
model
Multicollinearity
testing
Covariate i
LA emigration estimates
constrained to sum to
the relevant NMGo
estimate
Final model
Covariates
selected by
stepwise
model in more
than one year
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)
2001 Census
Annual Population Survey
Population Statistics
Division, ONS
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 (+)
LA emigration
estimates
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 (+)
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 timeperiod
- 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
Emigration model specification
LA level data
IPS estimate of
LA emigration
(3 year average)
Covariate i
Covariate 1
Covariate 2
Covariate 3
Covariate 1
Stepwise
model
Multicollinearity
testing
Covariate i
LA emigration estimates
constrained to sum to
the relevant NMGo
estimate
Final model
Covariates
selected by
stepwise
model in more
than one year
Updated model for year ending mid-2012
emigration estimates at LA level
2011 Census
Annual Population Survey
Number of hostels (+)
Migrant Worker Scan
Number of people of North American country of
birth (+)
Number of people of Oceania country of birth (+)
LA emigration
estimates
Number of people of African country of birth (+)
Number of in-migrants of EU8 nationality (+)
Number of people aged 16+ in employment (-)
Modelled emigration estimates
<250
250-499
500-749
750-999
1,000-1,999
2,000-3,999
4,000-6,999
>7,000
Modelled estimates of emigration
from local authorities in England
and Wales, year ending mid-2011
• Range from ca. 20 to
8,000
• Higher emigration flows
associated with London
and the larger regional
cities
Emigration as % of LA population
<0.20
0.20-0.34
0.35-0.49
0.50-0.74
0.75-0.99
1.00-1.49
1.50-2.49
>2.50
Modelled estimates of emigration
as a percentage of local authority
population, year ending mid-2011
• 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
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 ?