Download - Population and Migration Seeking your views Welcome and introductions Centre for Demography
Population and Migration
Seeking your views
Welcome and introductions
Centre for Demography
Population and Migration
Welcome and Introduction
ONS Centre for Demography
Centre for Demography
Aims of the day
• Communicate the latest work being carried out to improve population statistics through– the 2011 Census and – the Improving Migration and Population Statistics
programme
• Census– progress on planning and executing the 2011 Census– methodology for assessing coverage– quality assurance of the census population estimates
• Improving Migration and Population Statistics– present the indicative impacts– explain user engagement process– provide chance to feedback on results
AGENDA am
• 9.30 - 10.00 Registration and coffee• 10.00 Welcome and introduction to the day • 10.15 Census overview
– This session will provide an overview of the census components that are key to producing Census population estimates
– To provide an update on progress on recent events, such as the census rehearsal.
• 10.45 Census coverage– This will cover the methodology being developed to assess census coverage– It will focus on improvements that address many of the lessons from 2001
• 11.15 – 11.30 Coffee break• 11.30 Census data quality assurance
– To provide an update on Census data quality assurance plans– To summarise the processes and evidence to be used to validate Census local
authority estimates• 12.00 Questions• 12.30 – 1.15 Lunch
Agenda pm
• 12.30 – 1.15 Lunch• 1.15 Improving Migration and Population Statistics
Session I– Introduction and Background– User engagement– Indicative Impacts
• 2.30 – 2.45 Tea Break• 2.45 Improving Migration and Population Statistics
Session II– Open discussion
• 4:00 Close
High level timetable
• 18 January 2010– Final date for comments
• 27 May 2010– Revised 2002-08 population estimate for LAs– 2008-based Subnational Population Projections
• 27 March 2011 – Census day
Domestics
• Fire Exits• Fire Alarm• Refreshments
Tea and Coffee about 11:15
Lunch at about 12:30
Tea and Coffee about 2:30
Close at about 4:00
• Toilets• Delegate Packs• Questions
2011 Census Overview
Garnett ComptonONS Demography Seminar - December 2009
Introduction
• Reminder – key design changes• Where are we now?
• Census rehearsal• Census address register• Census legislation• Census stakeholder engagement• Census outputs
• Key milestones
What’s new since 2001?
• Questions• New Qs on population characteristics• New Qs on population base
• Address register• Field operation
• Distribution via post• Distribution of field staff• Questionnaire tracking
• Internet data capture
Census rehearsal areas
Rehearsal areas:• Lancaster – 62,000 • Newham – London – 40,000 • Isle of Anglesey – Wales 34,000
Small scale test:• Birmingham – 17,000
Objective:
• To validate 2011 Census field procedures and supporting systems
Rehearsal systems/procedures
• Recruitment of field staff• E-learning• Flexible deployment of field
staff• Questionnaire Tracking• Publicity• Local Authority &
Community engagement• Census coverage survey
Rehearsal systems/procedures
• Address register • Printing• Royal Mail delivery & collection• Internet completion• Public contact centre• Online help systems• Census Management
Information System
‘best internet survey I’ve ever seen’ – Prof Phil Rees
Rehearsal publicity
Engaging Advertising
• Reaching students and young people where they spent their time with some engaging advertising
Total Returns by Completion Method
(up to 29 November)(provisional)
0
10000
20000
30000
40000
50000
60000
Num
ber
of Q
uest
ionn
aire
s
All
Postal
IDC
REHEARSAL RESPONSE
• 35% overall (so far – 29/11)
• Action taken to improve response• More staff in Newham• More community liaison• More advertising• Targeted letters/questionnaires
• Possible reasons – logistical• postal delays (stuck in system?)?• time of year?• contact patterns?
• Possible reasons – behaviour• lack of trust?• not important – voluntary?• lack of awareness?
21/10 29/11
Anglesey 34% 42%
Lancaster 30% 39%
Newham 10% 21%
Overall 25% 35%
Birmingham 11% 21%
Rehearsal – some early thoughts (1)
What worked well:
• Recruitment, pay and training• Daily receipting• Questionnaire tracking system
• Linking replacements/deactivating addresses• Generating follow-up lists
• Internet data collection/Web self help• Actions to improve response rates
Rehearsal – some early thoughts (2)
What needs reviewing and refining:
• Understanding low response rates• Targeting of initial field resource• Mixture of full and part-time hours• Training and doorstep messages• Management information
• Specification of reports
• Improve awareness and routing to IDC• Working with LAs to increase publicity
Where are we now
Address register
• Data sent to suppliers for resolution(Royal Mail, Intelligent Addressing)
• Unmatched addresses sent to LAs• Address check implementation started
• In the field May – Aug 2010• 15% of postcodes targeted on mismatches and multi-
occupation
• Strong focus now on communal establishments• Prioritised for target populations – 3rd party suppliers• Special address check staff covering all of E&W
Number of mismatched addresses sent to LAs for resolution
0
50
100
150
200
250
0-499 500-999 1000-1499
1500-1999
2000-2499
2500-2999
3000-3499
3500-3999
4000 ormore
Number of mismatched addresses
Nu
mb
er
of
LA
s
Census legislation
• White Paper - 11 December 2008
• Census Order – tabled 21 October 2009
• Debated by the Delegated Legislation Committee - 30 November
• Full Lords debate – 2 December
• Privy Council - likely 10 Feb
• Census Regulations – March 2010
• EU legislation
LA engagement - foundations
• Stakeholder website launched September• New LA engagement advisory groups initiated
• Operational advisory group• Communication advisory group
• Local authority partnership guide launched October• Local authority communication toolkit• Regional networks established by many census
regional champions• Online communities of practice
What’s next for LAs?
• Second round of regional meetings hosted by CRCs• Regional meetings for LA communication teams to
launch toolkit and councillor handbook• Defining the ways of working during the operational
phase• Local partnership plans to agree commitments by each party
around– Media relations and publicity– Community liaison– Support with logistics– Ongoing contact mechanisms
Community liaison
• Liaison with national organisations representing target population groups continues
• Some good offers of help and support• Communication materials for community groups to use
being developed for March 2010• 40 Community advisors start September 2010 to liaise
with black and ethnic minority target population groups• Partnership plan with LA will also cover community
liaison activities
Census outputs - vision
• Web as the primary dissemination route• Flexibility for end users to create own products• Bulk download of data via the web
• Web functionality provided jointly with external partners
• 2001 comparisons which exploit stable geography (OAs)
• Microdata products provided via secure mechanisms
• UK Wide Approach with common disclosure control
Outputs – next steps• Continue technical development
• Demonstrate Prototype & agree partnership proposals Spring 2010• Populate 2011 System with some 2001 data December 2010
• User Consultation Round• Main content consultation in Dec 2009 • Geography consultation in Dec 2009• Publish Proposed 2011 Outputs Product set end- 2010
• Disclosure Control• UKSDC approach agreed September 2009• Complete alignment of Disclosure Control/Technical constraints and
User requirements Summer 2010
• Finalise proposals for• Microdata delivery• Analytical Uses
Census – milestones
2010 2011
Sep-09 - Dec-09Census Rehearsal
Oct 09 - Jan 10Census Order ?
May - SeptemberAddr. Checking Field Activity
Mar 11 - Jun 11Census Field Operation
27 March, 2011Census Day
MarchField staff recruitment starts
AugustArea Managers start work
2012Processing continues until April 2012
MayCensus Coverage Survey starts
NovSystem Readiness testing starts
JunFirst delivery of data
Jan - FebCensus Regulations?
Finally ……
• Coverage adjustment
• Quality assurance
• Quality census relies on other key aspects:• Address register• Census Operations:
– Questionnaire tracking– Publicity– Recruitment– Field operations and procedures
Thank you
Questions?
AGENDA – Census Coverage
1. Background2. Coverage in the 2001 Census3. 2011 Methodology overview4. Key changes5. Summary
WHAT IS THE PROBLEM?
• Despite best efforts, census won’t count every household or person
• It will also count some people twice
• Users need robust census estimates - counts not enough
• In 2001:– One Number Census (ONC) methodology was developed to
measure undercount– estimated 1.5 million households missed– 3 million persons missed (most from the missing
households but some from counted households)– Subsequent studies estimated a further 0.3 million missed
• In 2011 we want to build on the ONC, as broadly it was successful
2001 CENSUS UNDERCOUNT BY AGE-SEX
Underenumeration of Census by agegroup
0.0%
2.0%
4.0%
6.0%
8.0%
10.0%
12.0%
14.0%
16.0%
0 1-4 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84 85+
Agegroup
ON
C/C
en
sus
Males Females
RESPONSE RATES BY LOCAL AUTHORITY
COVERAGE ASSESSMENT PROCESS OVERVIEW
Estimation
Matching
Adjustment
2011 Census
Quality Assurance
Census Coverage
Survey
AREAS OF IMPROVEMENT• Elements of CCS Design• Estimation methodology• Measuring overcount• Adjustments for bias in DSE• Imputation
• Motivated by:– lessons learnt from 2001– 2011 Census design e.g. use of internet
THE CCS DESIGN
• Similar to 2001 CCS:– 300,000 Households– Sample of small areas (postcodes)– 6 weeks after Census Day– Fieldwork almost identical
• Improvements:– Designed at LA level, not for LA groups– Refined Hard to Count index (5 levels) using up to date data
sources– Use Output Areas as PSUs– Select 3 postcodes per OA– Revised allocation of sample (using 2001 patterns)
THE CCS DESIGN (2)
• What does this mean?– Each LA will have its own sample – at least 1 OA for each
hard to count level– Sample is more skewed to LAs with ‘hardest to count’
populations (with an upper limit of 60 OAs)• More LAs will have estimates based on their own data
• Especially in London and for big cities
– HtC index will be ‘up to date’– Most LAs will have 3 HtC levels
• Most London areas only had one in 2001
• Will be a 40%, 40%, 10%, 8%, 2% distribution
MATCHING AND ESTIMATION
• Estimation based on Dual System Estimation• Used mainly for wildlife applications• Requires two ‘counts’ of the population• Requires the two counts to be matched
• Use standard survey estimation techniques to generalise the DSEs to the whole population• Ratio estimator
• Trout, Catfish & Roach provides a fishing example of the principles of the method – Available in delegate packs
ESTIMATION
• Obtained lots of data from 2001 to be able to explore whether improvements can be made
• One issue was at what level to estimate undercount to best fulfil the assumptions of the methodology (Postcode, Groups of Postcodes)
• One key issue was whether we should group LAs by geography or by ‘type’
• Improvements:• Confirmed that using DSE at OA level is sensible• Confirmed that we should group LAs by geography• Use simple Ratio estimator• Confirmed that 2001 LA estimation method is still
best
ESTIMATION (2)
• What does this mean?– The estimation methodology is much the same as it
was– Should be slightly easier to explain– We will group LAs that don’t have enough sample
with their neighbours until that group has enough sample
– More LAs will have enough sample to produce direct estimates
OVERCOUNT
• In 2001, estimated around 0.4% overcount (duplication)– No adjustments made– Not integrated into methodology
• For 2011, expecting overcount to be higher– More complex population– Use of internet in 2011 Census
• Strategy is to:– A) Build a process to identify and remove obvious cases
(multiple response resolution)
– B) measure and make net adjustments on the remainder
– i.e. for the latter we are NOT removing duplicates
OVERCOUNT (2)
• Methodology:– Select targeted samples of census records
• Second residences• Students• Children
– Very large sample (~600,000k records)
– Automatic matching algorithm to identify duplicates
– Clerical checking of matches• expect to see ~13,000 duplicates• Also use the LS to QA the estimates
– Estimation of duplication rates by GOR and characteristics• estimating which is the correct record
– Why not do whole database and remove them?• High risk of making false positives and thus removing too many!
OVERCOUNT (3)
• What does this mean?– Population estimates will be reduced where there is overcount
– We will be able to say how much adjustment was made due to overcount
– The duplicates will still be in the data, we just won’t impute as much for undercount
DSE BIAS ADJUSTMENTS
• Assumptions underpinning DSE:– Homogeneity
– Independence
– Accurate Matching
– Closure
• DSEs usually have some bias, mostly due to failure of homogeneity assumption
• In 2001 Census we made a ‘dependence’ adjustment
• This showed that we need to have a strategy for measuring this
DSE BIAS ADJUSTMENTS (2)• Mitigate as much as possible:
i. Post-stratify DSE so heterogeneity is minimised
ii.Independence in CCS field processesiii.Design Matching to get accuracyiv.Collect CCS on same basis as Census
• Measure remaining bias– Specific adjustments – e.g. Movers, Overcount– Residual biases global adjustment
• Improved adjustment using Census address register
• Looking at improving age-sex distribution
DSE BIAS ADJUSTMENTS (3)• What does this mean?
– We will be making adjustments to the estimates based on plausible external data e.g.• Household counts• Sex ratios
– This will be part of the methodology– Also can be used if QA determines estimates are implausible
– Haven’t ruled out triple system estimation
COVERAGE ADJUSTMENT
• Imputation methodology had problems converging– Sometimes resulted in poor quality results
• Improvements:– Model characteristics at higher geographies– Allows more details to be modelled– Some additional topics in the CCS included in
models:• Migration variable (internal, international)• Country of birth (UK and non-UK)
– Non-controlled variables imputed by CANCEIS
• What does this mean?– Better Imputation quality– Characteristics of imputed improved
SUMMARY
• Coverage assessment is an integral part of the 2011 Census
• It will again define the key census outputs (estimates at LA level by age and sex) and adjust the database
• We learnt a lot of lessons in 2001 and have been working to address them
ESTIMATION results
Table 1: Overall relative bias (%) for simple ratio estimation method with DSEs at various levels
Estimation Area DSE Level LB LJ NX KK WB KO NA SH Total Perfect CCS 0.61 0.28 0.14 0.34 0.30 0.07 0.20 0.12 0.27 Postcode -1.99 -0.56 -0.84 0.05 0.07 -0.14 0.00 -0.07 -0.46 Cluster -0.58 -0.08 -0.29 0.25 0.23 -0.01 0.08 0.05 -0.05 Hard to Count -0.28 -0.08 -0.16 0.24 0.24 -0.03 0.10 0.08 0.01 2001 robust DSE -1.59 -0.42 -0.62 -0.05 0.05 -0.20 0.43 0.13 -0.31 Census -28.19 -13.33 -12.23 -8.01 -7.38 -6.08 -4.85 -4.09 -10.92 2001 Undercount -24.80 -12.90 -8.50 -6.50 -4.40 -5.90 -3.40 -2.40 Table 2: Overall RRMSE (%) for simple ratio estimation method with DSEs
at various levels
Estimation Area DSE Level LB LJ NX KK WB KO NA SH Total Perfect CCS 2.31 1.43 1.37 1.19 1.14 0.89 0.84 0.82 0.50 Postcode 2.93 1.48 1.56 1.12 1.08 0.88 0.78 0.80 0.56 Cluster 2.35 1.44 1.41 1.20 1.14 0.90 0.80 0.82 0.50 Hard to Count 2.35 1.43 1.40 1.20 1.13 0.89 0.81 0.83 0.50 2001 robust DSE 2.58 1.35 1.43 1.06 1.03 0.83 0.94 0.80 0.51
Other results
Table 3 – Overall results comparison for the South East Region
EA Type Relative bias RRMSE95% Confidence Interval width Census Coverage
Contig 0.16% 0.33% 48418 93.4%
Noncontig 0.07% 0.31% 46128 93.4%
Table 7 – Overall results comparison for the North East Region
EA Type Relative bias RRMSE95% Confidence Interval width Census Coverage
Contig -0.01% 0.46% 22177 94.4%
Noncontig 0.06% 0.48% 23314 94.4%
Alternative non-
contiguous 0.01% 0.46% 22110 94.4%
Lessons learnt - One Number Census
• Not designed to be the lifeboat for a poor census
• Not robust enough to cope with extreme Census failures (Westminster)
• Not robust enough to cope with extreme changes in areas on the ground (Manchester)
• Correlation bias is a problem
• Overcount measurement was not adequate
2011 Aims and Objectives
• Measure undercount• Measure overcount• Address lessons from 2001• Take into account changes
- In census design- In those at risk of undercount
• Accuracy to be as good or better than in 2001- 0.2 per cent confidence interval nationally- 2 per cent on half million population total
2011 Census data QA: An update on planning and proposals for the validation of LA estimates
Louisa BlackwellPaula GuyGlen Doubleday
2011 Census & ONSCD Seminar on Population and MigrationDecember 2009
Contents
• Census data QA objectives
• Overview of the data QA: topic and demographic QA
• The QA Panel and its role
• The process for assessing and approving Census LA estimates; evidence and data
• Options for adjusting Census population estimates
• The LA consultation pilot
• Supporting analysis from 2009 to 2011
Census data QA objectives
• Ensure 2011 Census outputs are fit for purpose and meet user expectations
• Understand differences between Census population estimates and rolled-forward mid year estimates
• Ensure Census population characteristics are accurate
• Transparency
• Work in partnership with stakeholders
• Metadata including quality measures published with data
Topic QA
To quality assure detailed level Census data to address errors such as respondent or enumerator error or those introduced by processes such as data capture, edit or imputation. Includes item-level data, low level geographies and multivariate analysis of specified population subgroups.
Demographic QA
To quality assure national, regional and Local Authority District census estimates, drawing on external sources, using demographic indicators and guided by the input and direction of an expert QA panel
Demographic and Topic QA
Data load
Apply derivations & filters
Item imputation
Coverage estimation
Coverage imputation
Post-adjustment imputation
Apply complex DVs
Assign output geographies
Disclosure control adjustment
Demographic QA Topic QA
Data flows: Questionnaire tracking, Address Register, Field reports, Administrative and Survey sources
Reconcile multiple responses within a HH
Scanning & recognition
Internet data capture
The QA Panel and its roleRole: To assess Census population estimates at LA / regional /
national levels and recommend acceptance / rejection or further research
Membership– Head of the ONS Census Design Authority (Chair)– Head of Census Quality Team– Methodology Division experts in coverage adjustment– ONS Centre for Demography experts in mid-year population
estimation and projection– Independent expert demographers– Other relevant parties, such as representatives of the LGA,
NISRA, GROS, WAG and non-UK member(s)
The QA Panel indicative timetable
Key dates Meetings / Activities
July 2010 - July 2011 Quarterly to agree terms of reference, methods and data
July 2011 - Feb 2012 Weekly to agree LA estimates
Feb - March 2012 Overcount, visitor, second residence reconciliation agreed
March - May 2012 Final LA, regional and national estimates approved
Local Authority checking process - overviewLevel 1• Basic set of checks that all LAs go through
Level 2• Additional suite of checks tailored to address particular data problems
in LAs that didn’t pass level 1
Level 3• Final checks, following any adjustments/ contingency action and
following post-coverage adjustment item imputation
National / local reconciliation• Cumulative checks above LA level and other geographies
LA estimate
Level 1 checks
QA PanelreviewsLA estimates along with national and local reconciliation
LOCAL AUTHORITY ESTIMATES QA PROCESS
Level 1 checks (against comparators)Demographic indicators:• Age / sex distributions, sex ratios, young and old dependency ratios,
fertility and mortality measures
Key estimates and distributions:• Households (vs. Address Register and Council Tax), household size,
ethnicity, students, internal and international migrants, armed forces
Local evidence:• Supplied by LAs and available via other sources
Qualitative/ quantitative evidence:• Census data processing diagnostics, Management Information and
LA profile information
LA sex ratios compared to England
0.4
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
Age
Se
x r
ati
o
MYE PR LB Ch B Sch C Pens MYE England
National / local reconciliation
Demographic indicators:• Internal, home country and international migration flows and patterns• Sex ratios, mortality and fertility rates
Data checks:• Cumulative counts• Multiple enumeration rates and reconciliations (eg visitors / usual
residents)• Population sub-group cumulative totals
Pause and review to check progress:• After approximately 20 per cent of LAs have been processed
Implement adjustment options
LA estimate
Level 1 checks
QA PanelreviewsLA estimates along with national and local reconciliation
Level 2 checks
QA Panel
Rejects
QA Panel
Accepts
Proceed to imputation
LOCAL AUTHORITY ESTIMATES QA PROCESS
QA Panel Provisional Acceptance
Level 2 checks
Address Register / Questionnaire Tracking analysis:• Reconciliation against dummy forms and source updates, CE counts
and second address counts
Demographic indicators:• Household size by ethnic group
Administrative source comparisons for key population sub-groups:• Students, armed forces personnel, gypsies and travellers, school
children pensioners, migrants, etc.
Options for adjusting Census population estimates• Alternative post-stratification of the Dual System Estimation
• Alternative post-stratification of areas• Borrow strength between areas• Use visitor / multiple enumeration / student reconciliations to revise
populations in the coverage assessment process• Calibration to:
– national sex ratio etc– alternative administrative source – estimate from analysis of Longitudinal Study members
• Triple System Estimation
Implement adjustment options
LA estimate
Level 1 checks
QA PanelreviewsLA estimates along with national and local reconciliation
Level 2 checks
QA Panel
Rejects
QA Panel
Rejects
QA Panel
Accepts
Proceed to imputation
LOCAL AUTHORITY ESTIMATES QA PROCESS
Level 3 checks
QA Panel recommendation to
ONS senior managers
QA Panel Provisional Acceptance
QA Panel
Rejects
Level 3 checks
• Applied on the fully adjusted Census database
• Provide a check on the plausibility of estimates for key population sub-groups
• Include validation of key variables / distributions
• Final check on demographic indicators
LA engagement objectives for Census QA• To improve LAs’ understanding and confidence in the Census
resultso Presentation of Census QA information at stakeholder eventso Feedback received at working / advisory groupso Publication of key materials
• To develop the best possible understanding of each LA’s population ahead of the Census
o Census Liaison Manager user guideo QA studieso LA pilot
LA engagement key tasksTask Date
ONS contacts pilot LAs and requests data Dec 09
Pilot LAs send intelligence to ONS End Jan 10
ONS assesses evidence and evaluates pilot Mid March 10
ONS begins QA studies Early April 10
LAs in QA studies return intelligence for assessment End June 10
Remaining LAs provide intelligence to ONS End Sept 10
ONS assesses remaining LAs intelligence End March 11
Indicative timetable for 2009 - 2011 analysis plan
Analysis plan in preparation for LA validation / contingency
Analyses Pilot LAs QA studies Remaining LAs
Level 1 checks Oct 09 - Mar 10 Mar 10 - July 10 July 10 - Dec 10
New administrative microdata*
Oct 09 - Mar 10 Mar 10 - July 10 TBA
Data matching pilots
Feb 10 - May 10
TBA TBA
*School Census, HESA, Migrant Worker Scan, Patient Registers, DWP LS Master Index, Welsh School Census, Project Semaphore, Claimant Count Cohort, GENSERV
CLOSE
Comparator data
0 10 20 30 40 50 60 70 80 90
Age coverage (0 to 90+ years)
Super older person databasePension credit claimants
Electoral register2001 CensusPrisoner data
Unemployment benefit claimsHome armed forces data
Foreign armed forces dataHigher education students data
School CensusChild benefit claimants
Population estimates byPatient register
Population estimates by ethnicRolled forward MYEs
Age coverage of Administrative Sources for 2011 Validation
Improving Migration Statistics
ONS Centre for Demography
Centre for Demography
Indicative impacts
• Impacts are indicative– so will change before final publication in May 2010
• Revisions are distributional– No significant effect at England and Wales level– Improving internal and international migration
distributions
• Aim is successive improvements to estimates at LA level– So better comparison to 2011 Census
Distribution of impact across all local areas 2002 to 2008
Camden has been excluded from this chart
02
04
06
08
0N
umb
er o
f Loc
al A
utho
ritie
s
-6 -4 -2 0 2 4Percentage Impact
Cumulative percentage revision to mid-2008 population as a result of improvements to migration estimates
Background
• Importance of migration: – Key component of population change– Changing society– Economic situation
• Drivers for improvement work: – relevant statistics– multiple purposes and customers– timeliness, quality
• Census provides benchmark– Migration estimates used to measure population
between censuses
Migration: Front page news
Context - Change
UK Components of Change 1998 to 2008
0
50
100
150
200
250
300
1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008
Thousands
Net migration & other changes
Natural change
UK Components of Change 1998 to 2008
0
50
100
150
200
250
300
1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008
Thousands
Net migration & other changes
Natural change
International moves.Over seven years mid-2002 to mid-2008
Internal moves across an LA boundary.Over seven years mid-2002 to mid-2008.
Vision
Migration and Population Statistics meeting user needs:- At the right time- Covering the relevant populations- Measuring change accurately (national and local)- Detecting turning points
And are trusted as authoritative:- Based on range of developed best up to date sources- Enhanced, transparent, sustainable, statistical methods- With quality measures
By highly engaged users
Improvements already delivered
• Improvements to methods in 2007 – distribution of migration, emigration modelling
• Improved port survey– Better coverage of migrants at key ports in IPS
• Improved migration reporting– Quarterly report and less confusion on multiple outputs
across government
• Indicators of migration and improved timeliness• National Estimates of short-term migration
Early indicator of migration
Issues Addressed By Improvements
1. Internal migration (within England & Wales)• Internal migration estimates dependent on all
individuals re-registering quickly with a GP when they move
• Some students are slow to re-register when they move to university and/or when they move at the end of their studies
2. International immigration • 2001 Census data currently used to distribute
immigration between local areas• Doesn’t reflect changes between 2001 and 2008
Improvements that change previously published numbers
• Student adjustments using HESA data– HESA data of student residential (term-time) addresses– Compare against GP lists by single year of age and sex– Adjust where current data underestimates student flows
• Distribution of international immigration using administrative and other sources– Using a model to replace Census data
• Refined model for emigration data– Listened to comments on earlier model– Learned lessons from immigration modelling– New model better reflects nature of data– Immigration main driver for emigration distribution
The Future
• More extensive use of administrative data for statistical purposes– More data sharing gateways– Linking and matching between sources
• Use of new data sources– e-Borders roll-out
• Better quality measures– Ability to make statements about confidence in figures
• 2011 Census– Basis of estimation for the next decade
User Engagement
Centre for Demography
Overview
• Aims of user engagement• Timetable• Supporting material• How to respond• What we’ve learned from QA groups• Refinements
Aims of user engagement
• Provide all users with the opportunity to comment and ask questions
• Seek user responses to specific questions
• Document clearly the changes being made and the indicative impacts
• Concurrent user engagement - Consultation on subnational population projections for England
Timetable
• User Engagement- 30 November to 18 January
• BSPS Discussion Session on Improvements- 7 January (Leeds) & 11 January (London)
• Final Impacts Summary- March/April
• Publication of Subnational Population Projections & Revised Mid-year Estimates (mid-2002 to mid-2008)
- 27 May
• Publication of Mid-2009 Population Estimates- 24 June
Key documents published on November 30
www.statistics.gov.uk/imps
• Introduction paper• Overarching paper• Feedback form on the improvements• Impact paper• Impact tables & charts• Frequently asked questions
Supporting Documentation Published
www.statistics.gov.uk/imps
• Students adjustment & migration modelling• Methodology papers• Impact assessments and validation• Further work
• Other Reports• Assessment of Demographic Rates• Review of QA Activities• Report on International Students in Communal
Establishments• Local Area Short-term Immigration Estimates• Report on change to use of Irish migration data
How to respond
• Feedback questionnaire
• Responses supported by relevant information
• Questions for clarification
Feedback Received from QA Groups
• Local Insight Reference Panel (LIRP)• Tees Valley • London • Kent • Birmingham • Oxford • Bristol • Milton Keynes
• Expert Peer Review Group• Pete Boden (University of Leeds)• Paul Williamson (University of Liverpool)• James Raymer (University of Southampton)• Tony Champion (University of Newcastle)
Feedback from LIRP
• Overall• Fertility rates are a useful way of demonstrating impacts• Impacts are generally plausible but some changes more
difficult to interpret
• Migration Modelling• Issues with sources used in models• Scope for changing ‘intermediate geographies’• Need for more technical information
• Student Adjustment• Total population of students would provide useful context• Student adjustments look plausible in areas with large
student populations
Feedback from Expert Group
• Overall• Appreciated need for proposed improvements• Recommended a framework to consider migration • Regional immigration methods need further research
• Migration Modelling• Complexity / accuracy balance• Constraining model based estimates• Broadening models – across years and/or combining
immigration and emigration
• Student Adjustment• How census data was used in the adjustment• Clarification on double counting moves
• Short-term Migration• Definition used and seasonality in series
Refinements
• Migration Modelling• Intermediate geography?• Additional factors entered into models• Refinement of factors already entered
• Student Adjustment• Proportion of foreign students remaining in UK after studies• Imputation of term-time address• Area specific issues – Warwick/Coventry
• Final Impacts of Methodological changes• March/April
2008-based Subnational Population Projections
• Trend based projections for England– covers years 2008 to 2033 (25 year period)– reflect indicative mid-2004 to mid-2008 population estimates– produced for GORs, LAs, PCOs and SHAs– consistent with National Population Projections
• Available for CLG and DH to use in resource allocation
• Incorporates improvements to projections methods
• Consultation on migration assumptions – 30 November 2009 to 18 January 2010
Improvements to Migration and Population Statistics
Indicative impacts
Centre for Demography
Indicative impacts
• Indicative impacts • How revisions have an effect• Distribution of revisions• An example of components of change• Areas with biggest Changes• Camden - a case study• Demonstrating an improvement
Indicative impacts
• Impacts are indicative– Data will change– Small changes in most areas– Some areas may change substantially
• Impacts will change because of– Further work– Results of the comments received– Final LA results
• summary will be published March/April 2010• full results will be published May 27 2010
How the changes have an effect
Difference in 2008 population estimates ->
Cumulative change to migration data
Subnational Population Projections
Other Population Statistics
Other Statistics
Students Data
Internal Migration
International migration
Mid-year population estimates
Components of change
• Each revision +ve or –ve• Revisions interact• Changes data from 2002 to 2008
• Students adjustment to internal migration–Moves to university–Moves after university–Double counting adjustment
• International migration–Modelling in-migration–Updated out-migration model
• Other changes (small)
Distribution of impact across all local areas 2002 to 2008
Camden has been excluded from this chart
02
04
06
08
0N
umb
er o
f Loc
al A
utho
ritie
s
-6 -4 -2 0 2 4Percentage Impact
Cumulative percentage revision to mid-2008 population as a result of improvements to migration estimates
Cumulative revision to mid-2008 population as a result of improvements to migration estimates
Changes at local authority level
• Changing distribution of internal and international migration at LA level
• Biggest cause of change at LA level tends to be international migration re-distribution– But notable exceptions
• Cause of change shown in Table 2– In delegate packs.
Example – Manchester
Cumulative revisions 2002 to 2008
Centre for Demography
Manchester revisions
Revisions:Net student: 5,700Net international: -1,700Other Changes: 500Total revision: 4,500
Manchester revisions
Revisions:Net student: 5,700Net international: -1,700Other Changes: 500Total revision: 4,500
-50,000
0
50,000
100,000
150,000
200,000
250,000
300,000
Immigration
Revision
Original
Manchester revisions
Revisions:Net student: 5,700Net international: -1,700Other Changes: 500Total revision: 4,500
-50,000
0
50,000
100,000
150,000
200,000
250,000
300,000
Immigration
Revision
Original
-50,000
0
50,000
100,000
150,000
200,000
250,000
300,000
Emigration
Revision
Original
Manchester revisions
Revisions:Net student: 5,700Net international: -1,700Other Changes: 500Total revision: 4,500
-50,000
0
50,000
100,000
150,000
200,000
250,000
300,000
Immigration
Revision
Original
-50,000
0
50,000
100,000
150,000
200,000
250,000
300,000
Emigration
Revision
Original
Manchester revisions
Revisions:Net student: 5,700Net international: -1,700Other Changes: 500Total revision: 4,500
-50,000
0
50,000
100,000
150,000
200,000
250,000
300,000
Immigration
Revision
Original
-50,000
0
50,000
100,000
150,000
200,000
250,000
300,000
Emigration
Revision
Original
Manchester revisions
-50,000
0
50,000
100,000
150,000
200,000
250,000
300,000
Inflow
Double Counting
Post study
To study
GP List
-50,000
0
50,000
100,000
150,000
200,000
250,000
300,000
Outf low
Double Counting
Post study
To study
GP List
Revisions:Net student: 5,700Net international: -1,700Other Changes: 500Total revision: 4,500
-50,000
0
50,000
100,000
150,000
200,000
250,000
300,000
Immigration
Revision
Original
-50,000
0
50,000
100,000
150,000
200,000
250,000
300,000
Emigration
Revision
Original
Manchester revisions
-50,000
0
50,000
100,000
150,000
200,000
250,000
300,000
Inflow
Double Counting
Post study
To study
GP List
Revisions:Net student: 5,700Net international: -1,700Other Changes: 500Total revision: 4,500
Manchester revisions
Revisions:Net student: 5,700Net international: -1,700Other Changes: 500Total revision: 4,500 -50,000
0
50,000
100,000
150,000
200,000
250,000
300,000
Inflow
Double Counting
Post study
To study
GP List
-50,000
0
50,000
100,000
150,000
200,000
250,000
300,000
Outflow
Double Counting
Post study
To study
GP List
Manchester revisions
-50,000
0
50,000
100,000
150,000
200,000
250,000
300,000
Inflow
Double Counting
Post study
To study
GP List
-50,000
0
50,000
100,000
150,000
200,000
250,000
300,000
Outflow
Double Counting
Post study
To study
GP List
Revisions:Net student: 5,700Net international: -1,700Other Changes: 500Total revision: 4,500
Manchester revisions
-50,000
0
50,000
100,000
150,000
200,000
250,000
300,000
Inflow
Double Counting
Post study
To study
GP List
-50,000
0
50,000
100,000
150,000
200,000
250,000
300,000
Outf low
Double Counting
Post study
To study
GP List
Revisions:Net student: 5,700Net international: -1,700Other Changes: 500Total revision: 4,500
-50,000
0
50,000
100,000
150,000
200,000
250,000
300,000
Immigration
Revision
Original
-50,000
0
50,000
100,000
150,000
200,000
250,000
300,000
Emigration
Revision
Original
Biggest 10 percentage upward revisions by local authority
Population, thousands Current mid-2008 population
Cumulative revision
2002 to ‘08
Percentage revision 2002 to ‘08
Annualised percentage revision
Hounslow
Boston
Southwark
Peterborough
Crawley
Harrow
WokingSouth Cambridgeshire
Barnet
Great Yarmouth
223
58
278
164
101
216
92
139
332
94
11
3
11
7
4
8
3
4
10
3
5.0
4.7
4.1
4.0
4.0
3.7
3.2
2.9
2.9
2.8
0.7
0.7
0.6
0.6
0.6
0.5
0.4
0.4
0.4
0.4Excludes City of London and Isles of Scilly
Biggest 10 percentage downward revisions by local authority
Population, thousands Current mid-2008 population
Cumulative revision 2002 to ‘08
Percentage revision2002 to ‘08
Annualised percentage revision
Camden
Cambridge
Elmbridge
Forest Heath
Oxford
S’th Northamptonshire
Durham
Ceredigion
Rutland
Brent
236
123
132
65
154
91
96
78
39
271
-20
-7
-7
-3
-7
-4
-4
-3
-2
-9
-8.5
-5.7
-5.2
-5.1
-4.8
-4.3
-4.2
-4.0
-3.9
-3.5
-1.1
-0.8
-0.7
-0.7
-0.7
-0.6
-0.6
-0.6
-0.5
-0.5
National and regional indicative impact
population thousands Current mid-2008 population
Cumulative effect of change
Cumulative revision
2002 to ‘08
Annualised percentage revision
England and Wales
England
North East
North West
Yorkshire & Humber
East Midlands
West Midlands
East
London
South East
South West
Wales
54,440
51,446
2,575
6,876
5,213
4,433
5,411
5,729
7,620
8,380
5,209
2,993
10
13
-1
1
1
-5
-4
-16
58
-16
-4
--3
0.02
0.03
-0.04
0.01
0.02
-0.11
-0.07
-0.28
0.76
-0.20
-0.08
-0.11
0.00
0.00
-0.01
0.00
0.00
-0.02
-0.01
-0.04
0.11
-0.03
-0.01
-0.02
Formal Tables
• Summary Tables– Table 1: Total impact by year
• Table 1b: Biggest 20 increases, mid-2008• Table 1c: Biggest 20 decreases, mid-2008
– Table 2: Cumulative effect by adjustment, mid-2008• Detailed
– Table 3: Annual and cumulative students effect– Table 4: Annual and cumulative effect of net international migration– Table 5: Annual and cumulative effect of other changes
• Very Detailed– Table 6: Net and gross students effects, by type of flow
• (to study, post study, and counter adj.)– Table 7: Net and gross international migration– Table 8: Size of increase in student flows, by type of flow
• Context– Table 9: Short-term and long-term international immigrants, mid-2007
• Tables are by LA, county, GOR, etc, and for all years mid-2002 to mid-2008 (except where single year is indicated).
• Some material by age and sex available on request.
Charts Available
• All charts are by local authority
• Student adjustment and internal migration– Adjustment as percentage of student flows
• International migration– Net
– In
– Out
• Total change and total effect
• Total fertility rate
Case Study - Camden
Centre for Demography
Camden Births
Births in Camden 2001 to 2008
2600
2700
2800
2900
3000
3100
3200
2001 2002 2003 2004 2005 2006 2007 2008
Camden
Impact of proposed changes: Total Fertility Rate (TFR)
1.10
1.15
1.20
1.25
1.30
1.35
1.40
1.45
1.50
2001 2002 2003 2004 2005 2006 2007 2008
To
tal F
ertil
ity R
ate
(TF
R)
TFR published
Camden
Impact of proposed changes: Total Fertility Rate (TFR)
1.10
1.15
1.20
1.25
1.30
1.35
1.40
1.45
1.50
2001 2002 2003 2004 2005 2006 2007 2008
To
tal F
ert
ility
Ra
te (
TF
R)
TFR published
TFR incorporatingonly studentadjustment revision
Camden
Impact of proposed changes: Total Fertility Rate (TFR)
1.10
1.15
1.20
1.25
1.30
1.35
1.40
1.45
1.50
2001 2002 2003 2004 2005 2006 2007 2008
To
tal
Fer
tili
ty R
ate
(TF
R)
TFR published
TFR incorporatingonly studentadjustment revision
TFR onlyinternationalmigration revision
Camden
Impact of proposed changes: Total Fertility Rate (TFR)
1.10
1.15
1.20
1.25
1.30
1.35
1.40
1.45
1.50
2001 2002 2003 2004 2005 2006 2007 2008
To
tal F
ert
ility
Ra
te (
TF
R)
TFR published
TFR revised -including allrevisions
TFR incorporatingonly studentadjustment revision
TFR onlyinternationalmigration revision
Camden
Impact of proposed changes: Annual and cumulative population change
-25,000
-20,000
-15,000
-10,000
-5,000
0
2001 2002 2003 2004 2005 2006 2007 2008
Ch
an
ge
in m
id-y
ea
r p
op
ula
tio
n e
sti
ma
te
Annual revision
Cumulative revision
Camden
Impact of proposed changes: total mid-year population estimates
180,000
190,000
200,000
210,000
220,000
230,000
240,000
2002 2003 2004 2005 2006 2007 2008
Mid
-yea
r p
op
ula
tion
est
imat
e
Published mid-yearpopulation estimate
Revised indicativemid-year populationestimate
Camden
Impact of proposed changes: international migration inflow
-4,000
-2,000
0
2,000
4,000
6,000
8,000
10,000
12,000
2002 2003 2004 2005 2006 2007 2008Inte
rnat
ion
al m
igra
tion
inflo
w
Internationalmigration inflow -current
Internationalmigration inflow -revised
Inflow revision -migration modelling
Camden
Impact of proposed changes on internal migration: Student adjustment
-3,500
-3,000
-2,500
-2,000
-1,500
-1,000
-500
0
500
2002 2003 2004 2005 2006 2007 2008
Inte
rnal
Mig
ran
ts
Internal migration -current methods
Internal migration -after revision fromstudent adjustment
Revision - resultingfrom studentadjustment
Camden – student revisionstotal 2002 to 2008
Inflow Outflow Balance
To study
After study
Double counting
2,300
3,000
-1,700
1,000
3,300
-1,600
1,300
-300
-200
Net 3,700 2,700 800
Camden
Percentage of student flows adjusted
-100
-80
-60
-40
-20
0
20
40
60
80
100
Per
cen
tag
e o
f st
ud
ent
flo
ws
adju
sted
Student moves to study Student moves after study
Blue bars indicate f low s to the area
Red bars indicate f low s away from the area
From domicileresidence
To study residence
From studyresidence
To first destinationresidence
Demonstrating an improvement
Centre for Demography
Issues to be addressed by the new methodology…
• Some young people, particularly young men, not changing their GP registration soon after they move
• Students a sub-set of young people, who necessarily cluster in certain areas of the country
• Affects estimation of students moving to university and moving away after their studies
• Some encouragement to change GP registration at start of studies, but no encouragement when students leave
Solution: what’s new?
• Higher Education Statistics Agency (HESA) data
• Data on all HE students
• New term-time postcode detail collected by HESA for all institutions from 2007/08 academic year
• New detail received March 2009
Modelling in-migration
• Current method uses 2001 Census data to distribute to LA level
• Clear changes in migration trends since 2001
e.g. EU accession
• Concept proved with introduction of local authority out-migration models in 2007
What modelling achieves
• Improves timeliness at LA level
• Potential use of administrative data
• GP registrations (Flag 4s)
• National Insurance Number (NINo) allocations to overseas nationals
• Annually updated counts available
• Provide counts at local authority level
Demonstrating an improved methodology• Student adjustment uses data from an independent source that
gives actual student moves missed by patient registers• Student adjustments after study
– Carefully verified by other data– Based on known student numbers– Using distributions which have been carefully corroborated
• International immigration estimation model– Uses updatable sources to distribute instead of fixed 2001 Census
data– Model makes use of the best features from a range of administrative
and other sources– Minimises the impact of definitional issues with administrative sources
• International emigration model– Updated to reflect comments made previously– More technically robust– Better reflects data structure– Incorporates improved immigration data
Demonstrating an improvement
• Demographic analysis shows improvement in key areas (e.g. Camden)
• Analysis of student areas shows much more plausible age profiles after student adjustment (see June Roadshow slides)
Indicative results: Ceredigion mid 2007 population
0
500
1,000
1,500
2,000
2,500
3,000
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35
single year of age, 10-35
po
pu
lati
on
original
adjusted
adj+cadj3yrlag
2001 pattern
mid-2007
Quality assuring the improvement
• Giving all users a chance to comment• Extensive and rigorous internal quality
reviews• Using local insight to:
– Develop and refine methods– Sense check the results
• Extensive peer review
Short-term ImmigrationEstimates at Local Area Level
Centre for Demography
Introduction
• Local Authority level short-term immigration estimates published for first time in October 2009 as part of a research report
• Estimates are available for:• The year to mid-2007• In-flows only• Moves made for between 1 and 12 months• All reasons for visit (with a worker/non-worker breakdown
provided)
• England & Wales level estimates previously published for mid-2004 to mid-2007
Total Short-term visits: Top Ten Areas
Rank Local Authority Estimate
1 Westminster 62,800
2 Manchester 35,900
3 Birmingham 33,000
4 Ealing 29,200
5 Camden 28,000
6 Barnet 23,500
7 Brent 21,600
8 Southwark 21,300
9 Oxford 19,500
10 Wandsworth 18,800
Research Report
• Sets out detailed methodology• Data used• Differences between methods for workers and non-
workers• How final approach was chosen
• Summarises validation work• Statistical assessment of model validity/stability• Assessment by Reason for Visit• Assessment of areas with largest worker estimates• Use of HESA data for international short-term students
Regional Level Immigration Estimates
Region Estimate % of England & Wales Total
England 1,295,000 97%
North East 28,000 2%
North West 120,000 9%
Yorkshire & The Humber 85,000 6%
East Midlands 80,000 6%
West Midlands 97,000 7%
East 113,000 8%
London 480,000 36%
South-East 199,000 15%
South-West 92,000 7%
Wales 40,000 3%
Reason for Visit
Reason For Visit Estimate % of England & Wales Total
Work 175,000 13%
Study 199,000 15%
Visiting Friends or Family 538,000 40%
Join/Accompany 11,000 1%
Business 120,000 9%
Holiday 214,000 16%
Other 77,000 6%
Total 1,334,000 100%
Short-term Immigrant Workers: Top Ten Areas
Rank Local Authority Estimate
1 Newham 4,400
2 Brent 4,300
3 Ealing 4,000
4 Birmingham 3,600
5 Manchester 3,100
6 Haringey 3,100
7 Waltham Forest 2,900
8 Tower Hamlets 2,800
9 Hounslow 2,700
10 Wandsworth 2,600
Short-term International Students: Top Ten Areas from HESA data
Local Authority HESA Estimate of Short-term
Immigrant Students
% of Short-term Immigration
Estimate
Camden 5,200 19%
Manchester 4,000 11%
Cardiff 3,900 32%
Islington 3,900 25%
Newham 3,800 21%
Newcastle upon Tyne 3,800 40%
Coventry 3,200 30%
Birmingham 2,900 9%
Tower Hamlets 2,800 17%
Leeds 2,800 15%
Conclusions
• Current methodology and estimates are initial work
• Feedback is being sought from users to inform further research
• Aim to publish mid-2008 local authority estimates in May 2010