Handling Migration and Commuting Flow Data

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Handling Migration and Commuting Flow Data

• Day session at the ESRC Research Methods Festival
  at St Catherines College,
• University of Oxford, 2 July 2008

2

• Centre for Census Interaction Data Estimation and
  Research

3
Programme Morning session

• Data Issues and Estimation Methods
• Sources of interaction data in the UK
• Web-based Interface to Census Interaction Data
• Shortcomings of Census Interaction Data
• Estimating Spatially Consistent Interaction Flows
• Using Interaction Data from the SARs and the LS
• Measuring Ethnic Migration Using Commissioned Data

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Programme Afternoon session

• Analysis and Modelling Methods
• Migration and Socioeconomic Change
• Commuting in Rural Areas
• Modelling of Migration Flow Tables using Log
  Linear Models
• Poisson Modelling of Migration
• Spatial Interaction Modelling of Commuting to
  School
• Finding Clusters Among the 25 million Commuters
  in a Billion Cell Matrix

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Sources of Interaction Data in the UK

• John Stillwell
• Centre of Interaction Data Estimation and
  Research
• School of Geography, University of Leeds
• Presentation at the session on
• Handling Migration and Commuting Flow Data at
  the ESRC Research Methods Festival, St
  Catherines College, University of Oxford, 2 July
  2008

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Aims

• Research methods are frequently determined by the
  type of migration and commuting interaction data
  that are (not) available (macro/micro data)
• Important for researchers to know what data sets
  exist and what are the characteristics of the
  data from different sources
• CIDER undertook an audit of interaction data
  (Dennett et al., 2007, Working Paper 07/05,
  School of Geography, University of Leeds)
• This presentation is an overview of interaction
  data sources

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Presentation

• Types of data source
• Definition and measurement
• Census interaction data sources
• Administrative interaction data sources
• Survey interaction data sources
• Conclusions

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Interaction data sources

• Censuses of Population comprehensive and
  reliable migration and commuting data,
  particularly for flows within and between small
  areas
• Administrative records collection of records
  arising from some transaction, registration, or
  record of service delivery
• Social surveys samples of population allowing
  useful cross-classification at national
  (regional) level

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Definition and measurement

• Migration and commuting variables defined in
  different ways in different sources
• How is a migration defined? A permanent change of
  usual residence? What about those moving between
  residences on a temporary basis students, second
  home owners, etc
• How do we measure commuting? The journey from
  home to work? What about those who work in
  different places or those who travel from home to
  temporary accommodation for periods of work, etc

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We tend to think of migration and commuting in
the way they are derived from census questions

• These definitions and measures are particular to
  the census but there are different measures of
  migration e.g. migrants, wholly moving
  households, moving groups, representative persons
  of moving groups
• More generally, an important conceptual
  difference is between migrants/transitions
  (census data) and migrations/moves/events
  (registration data)

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Migrants versus moves Lexis representation
FBDE includes persons from the 1986-91 birth
cohort who were all aged 5-9 in 1996 and 10-14 in
2001 these are counts of exist-survive migrants
over the five year period. ABDF includes those
aged 10-14 during the period 1996-2001 (including
half those from the 1986-91 birth cohort and half
those from the previous cohort) these are counts
of moves over the five year period
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Main Census tables
Counts of migration are available from the
following tables Key Statistics Table 24,
Standard Tables 008 and 009 and Theme Table 033
But no tables on commuting
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Origin- Destination Statistics 2001 and 1991
Tony Champion, Robin Flowerdew
James Raymer
SMS SWS STS
Adam Dennett Oliver Duke-Williams Zhiqiang Feng
Martin Frost, Mike Coombes
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Migrants and commuters to Leeds from 2001 SMS and
SWS
Daily in-commuters in 2001
In-migrants in 2000-01
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Commissioned tables

• Customised output from the 2001 Census may be
  commissioned from ONS Customer Services when
  particular cross-tabulations are not available
  from the standard tables
• Commissioned tables incur charges to recover
  staff and material costs
• Once delivered and paid for by customer, each
  table listed on the ONS website and available to
  all users free
• All commissioned tables of 2001 data are subject
  to checks to ensure confidentiality - each table
  is subject to SCAM procedures and consequently
  inconsistencies will appear when checking totals
  with data from other census sources

Serena Hussain
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Samples of Anonymised Records

• Microdata relating to individuals or households
• 1991
• Individual SAR (2 sample)
• Household SAR (1 sample)
• 2001
• Individual SAR (Licensed) (3 sample)
• Household SAR (Licensed) (1 sample)
• Individual Controlled Access Microdata Sample
  (Individual CAMS)
• Household Controlled Access Microdata Sample
  (Household CAMS)
• Small Area Microdata (SAM) (5 sample)
• Spatial resolution is key issue with micro data
  for migration analysis, the 2001 SAM has the
  advantage of a detailed destination geography,
  although the origins remain as GOR

Paul Norman
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Longitudinal Studies

• Sources that contain multiple observations of a
  population of interest over a period of time
• ONS Longitudinal Study of England and Wales (LS)
• Scottish Longitudinal Study (SLS)
• Northern Ireland Longitudinal Study (NILS)
• These differ in a variety of ways including the
  length of the time period covered, the sampling
  fraction used, and the types of other data linked
  into the study
• New UK Household Longitudinal Study (UKLHS) -
  first wave of data collection in 2008 consisting
  of a wholly new sample of households (40,000), an
  ethnic minority boost sample, and a sample (up to
  100) drawn from the existing British Household
  Panel Survey (BHPS)

Paul Norman
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NHSCR data

• NHS Central Register (NHSCR) at Southport records
  movements of patients between Health Authority
  (HAs) areas in England and Wales and the Census
  Office has developed systems for capturing the
  reporting of re-registrations between areas
• Entries in the NHSCR include the date of birth,
  sex, the codes of origin HA and destination HA
• NHSCR data are movement data rather than
  transition data
• Time series available from mid-1970s but problems
  of changing administrative units/boundaries
  especially in late 1990s

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Changing patterns of net migration as shown by
NHSCR data
1988-90
1980-82
Source Stillwell (1994) Environment and Planning
A
22
Patient Register data

• NHSCR system in England and Wales only records
  movements between HAs - ONS has in the past used
  information from electoral registers and the
  census to apportion inflows and outflows between
  constituent local authorities (LADs)
• The inadequacy of the electoral registers in the
  estimation of sub-HA flows led ONS to investigate
  the patient registers held by every HA in England
  and Wales
• Registers contain the NHS number, gender, date of
  birth, date of acceptance at the HA and,
  importantly, the postcode of address, for each
  patient
• With postcode unit information being available,
  it is possible theoretically to create aggregate
  migration matrices for any level of geography

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Patient Register data

• Patient Register Data System (PRDS) contains an
  annual download from every patient register
• Comparing records in one year with those of the
  previous year by linking on NHS number enables
  identification of each person who changes their
  postcode
• Annual migrants rather than moves data
• Range of tables available from mid-1998 including
  flows between local authority districts by broad
  age group
• Scotland and Northern Ireland have independent
  systems

24
Comparison of PR and Census migration at district
level, England and Wales, 2000-01
IN
r 0.985
NET
OUT
r 0.987
r 0.783
25
Changing patterns of net migration as shown by
patient registration data
2005-06 balances
Changes in net balances 2000/01-2005/06
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PLASC

• Whilst the 2001 STS in Scotland provided
  details of the daily travel to study for students
  and children, similar data are not produced for
  England and Wales or Northern Ireland
• Pupil Level Annual School Census (PLASC)
  collects data from each local education authority
  (LEA) in England and Wales on the location of
  pupils and the schools that they attend

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PLASC data

• PLASC is the foundation of the National Pupil
  Database (NPD) and includes variables such as
  age, sex, ethnicity, free school meals and
  special education needs
• Linking of pupils from one year to the next using
  a unique pupil number (UPN) means that a
  longitudinal profile of each pupil is available
• Potential for pupils to be tracked over time and
  their transitions through the education system to
  be identified, including their movements between
  schools and between different home addresses
• PLASC data are therefore a potential source of
  data on (i) commuting to school, (ii) pupil
  mobility between schools and (iii) child
  migration from one usual residence to another

Kirk Harland
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Example of PLASC data for Leeds used to measure
residential migration and pupil mobility
Pupils moving home by age
Data source Education Leeds
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Hospital Episode Statistics (HES)

• HES data include details of all patient
  admissions to NHS hospitals in England from
  1989-90 onwards
• Each record holds around 100 personal, medical
  and administrative details of each patient
  admitted to hospital in England, including
  geographical information about the location of
  treatment and where the patient lived
• Around 12 million new records added to the
  dataset each year
• Requests for data in the form of database
  extracts or custom tabulations are made to the
  NHS Information Centre through their external
  data custodians, Northgate Information Solutions
• Potential source of information about commuting
  to hospital

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HES data Total number on in-patient visits
(including repeats) made to Yeovil and Weston
Hospitals from wards of England in 2000/01
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Surveys

• principal advantage is that they publish results
  with relatively high frequency often annually,
  but in some cases quarterly, allowing creation of
  data time series
• major drawback is the spatial resolution for
  published statistics - tends to be the GOR - so
  only very general patterns can be observed,
  despite the rich variety of other attributes that
  can be ascribed to the individual respondents
• the sample size of the survey is often relatively
  small, with implications for representativeness

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Conclusions

• Census products remain the most important data
  sources for migration and commuting flows but
  other sources, particularly administrative, have
  potential for greater use in interaction
  research e.g. patient registers, PLASC and HES
• Questions to be asked in next census for England
  and Wales on 27 March 2011 not yet agreed but
  might generate some new interaction data on
  migration or mobility of individual residents
  and on origins of visitors

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Questions from Test Census on 13 May 2007
http//www.statistics.gov.uk/ census/2011census/ C
ollectingtheInfo/ questionnairedevelopment.asp
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Beyond 2011

• 2011 is likely to be the last census in the UK
• ONS has proposals for an integrated population
  statistics system (IPSS) that combines census
  data at individual level into a single
  comprehensive statistics database with survey and
  administrative data and will underpin the
  countrys population and social statistics
• Includes a high quality address register
  containing information on properties and
  characteristics of individuals associated with
  these properties together with a population
  register, which will provide the basis for
  linkage with data from other sources
• If it happens, IPSS likely to be source of
  interaction data on a more regular basis - will
  be very important to ensure that data release is
  maximised without the effects of disclosure
  control becoming too detrimental