Aims of the Seminar

1. Population Estimates for England and WalesBSPS SeminarPopulation Estimates Unit&Improving Migration and Population Statistics (IMPS)www.statistics.gov.uk/popestwww.statistics.gov.uk/imps

2. Aims of the Seminar • To gain a better understanding of the population estimates methodology • To be aware of the sources used • To allow delegates to contribute ideas and expertise on two important issues relating to population estimates: ‘Quality Assurance’ and ‘Defining Usual Residence’. • To provide an overview of the work being undertaken as part of the Improving Migration and Population Statistics (IMPS) project.

3. Population Estimates - Overview • The ONS population estimates: • National level for England, Wales • Below national level, regions and local areas: including local authorities (LAs) and primary care organisations (PCOs) • By age and sex • By marital status • For total population and for household population • Annual one year in arrears (mid-2005 due to be published 24 August 2006)

4. Population Estimates - Definitions • The ONS population estimates are of the resident population and are as at 30 June • The national resident population is: • all those usually resident regardless of nationality • members of HM and US armed forces stationed in England and Wales. HM forces stationed overseas are not included. • Currently looking at new definitions e.g. daytime population, weekday population.

5. Population Estimates – Uses • The key uses of the population estimates: • Base for the population projections that are used for local government resource allocation • Also used as denominators in resource allocation • Planning by central and local government e.g. services for the elderly • Monitoring - used mainly as denominators in rates and ratios e.g. fertility and mortality rates • Grossing up survey results e.g. Labour Force Survey • Research by academics and others • Commercial Usage

6. Population Estimates – Methods 1 • Cohort component method: Pt = Pt-1 + Bt - Dt + It Population = Base (aged on) + Births - Deaths + net Migration • Most recent Census as the base (adjusted), • Then update annually by adding births, subtracting deaths and allowing for net migration • National and subnational, “top down”.

7. Population Estimates - Methods 2 Static Populations • These are sub-populations that don’t ‘age-on’ and are not covered by our estimates of Internal and/or international migration • Armed Forces, Prisoners, School Boarders Method • Remove these sub-populations (previous year) • Age on rest of population • Add in new sub-populations (current year)

8. Census as a base • Only complete enumeration of the population (especially at a person level) • Uses a similar definition of usual residence to the population estimates • Once a decade the population estimates are rebased using the most recent Census • Many distributions at local level are also based on Census data • Very accurate source

9. Births and DeathsSources • Birth Registrations • Provided by Vital Statistics Outputs Branch (VSOB) in ONS • Death registrations • Also provided by VSOB • Adjusted from age at death to give age as at mid-year (by VSOB)

10. BirthsMethodology • Births added on to population at age zero.

11. BirthsChallenges • Assume births abroad = births to non E&W residents • these births are allocated in proportion to the number of females of ‘childbearing age’ (15-44) • Births to non-resident mothers is a big issue. • Allocation of 0 year old migration. • Unlike deaths (more later) age at birth not an issue - not many people are born already aged 30!

12. DeathsMethodology • Subtract deaths from base BUT • January to June data are not final • So adjusted for late registrations by: • ‘adding on’ adjustments for previous year • assumes adjustments are small • assumes level of adjustments similar across years • avoids need for annual revision

13. ChallengesDeaths • Very accurate source - • but not perfect • Late Registrations (some now included) • Incorrect date of birth recorded • Deaths abroad vs. Deaths of non residents • Deaths ‘Elsewhere’ allocated in proportion to other deaths • Residence issues

14. Internal MigrationDefinitions Definition • A person who changes their place of usual residence within the United Kingdom • Internal migration is measured by looking at GP re-registrations • An Internal migrant is someone who • notifies their current GP of a change of address or • registers with a new GP in a different area from their previous GP

15. Internal MigrationSources 1 • National Health Service Central Register (NHSCR) • Moves between former HAs • General practitioners’ (GPs) patient registers • Lower geography but only annual download • Points to note • Reliant on registration with doctor • Possibly differing propensity to register • Time period is end July to end July (one month delay in registering allowed) • Armed forces and (currently) prisoners excluded

16. Internal MigrationSources 2 Combining the two sources: • Estimate moves between former health authorities for those aged one and over, from both sources • Derive scaling factors to apply to patient register data • Derive estimates for under-1s from estimates for one year-olds

17. International MigrationDefinitions • International MigrationCivilian migration between the UK and the rest of the world • International MigrantA person who changes his or her country of usual residence for a period of at least a year

18. International Migration – Overview 1 Total International Migration (TIM) estimates = International Passenger Survey migration data – Migrant Switcher adjustment + Visitor Switcher adjustment + Asylum Seeker adjustment + Irish flows

19. Irish Flows Asylum Seeker Adjustment Visitor Switchers IPS Migrants Migrant Switchers International Migration - Overview 2 Total International Migration

20. Irish (Eire) Flows • The International Passenger Survey (IPS) does not cover people crossing the Northern Ireland/ Republic of Ireland border • Therefore, an estimate of migrants to and from the Republic of Ireland needs to be made, using another data source • To avoid double-counting, any of these migrants captured by the IPS are removed from the IPS component

21. Irish (Eire) FlowsSources • Data supplied by Migration Statistics Unit: • by country & gender • provided by CSO(Ireland) • based on responses to the Irish Quarterly National Household Survey (April) • These estimates cover: • In migrants to Eire from E&W in the last 12 months • Out migrants to E&W who were living in Eire 12 months ago

22. Irish (Eire) Flows Methodology 1 • Split country totals to HA level - Using 2001 E&W Census Distributions Inflows: previous address 1 year ago in Eire Outflows: country of birth: Eire • Split HA totals to LA level Inflows: previous address 1 year ago in Eire (2001 E&W Census) Outflows: previous year resident population

23. Irish (Eire) Flows Methodology 2 • Apply age-sex distribution • Using data from the E&W and Irish Censuses • National age-sex distribution used Inflows: 2001 E&W Census Outflows: 2002 Irish Census

24. Asylum Seeker Adjustment Definition • Inflows are those coming into the UK claiming asylum: • who are granted asylum or • whose case will take 12 months or more to process • Outflows include people ‘removed’; people who have withdrawn their application and state their intention to leave; and an estimate of the proportion of ‘failed asylum seekers’ who leave • The ‘asylum seeker adjustment’ only includes asylum seekers missed by the IPS

25. Asylum SeekerSources • Migration Statistics Unit (from Home Office data): • AS inflow and outflow data for Principal & Dependent applicants: • UK by sex & quinary age groups • GORs • Home Office: • NASS (National Asylum Support Service) • Provides figures on subsistence and accommodation

26. Asylum SeekerMethodology Using the NASS data • For each LA calculate the number of AS in receipt of an allowance (either accommodation and subsistence or subsistence only) • Calculate the distribution within each GOR. • Also calculate the distribution for subsistence only recipients. • Assume 70% of AS applicants (and their dependents) in receipt of an allowance and the remaining 30% have a similar distribution to those receiving subsistence only

27. Asylum SeekersChallenges • Definition difference between Population Estimates and National Population Projections. • Use successful Asylum Seekers • Failed Asylum Seekers: Simply not sure where they go – is proportion correct? • Distributions: • Use of National age-sex distribution at LA level • Expanding quinary age groups using equal spread/ 85 cut-off

28. International Passenger Survey (IPS) • Continuous voluntary sample survey • Conducted by ONS since 1964 • Tourism, balance of payments and migration • Principle air, sea & Channel Tunnel routes • Approximately 0.2% of all travellers sampled - immigration filter shifts increase sample size • Based on intentions for ‘Length of Stay’

29. Migrant data IPS - ‘Length of Stay’ Question Visitor data

30. International Migration (IPS)Sources • Data provided by Migration Statistics Unit: • by age & sex • by HAs • High Weights data High Weights: Where 1 IPS contact is grossed to an excess of 1000.

31. International Migration Methodology 1 • Calculate GOR Totals - Aggregate IPS data (incl. high weights) to GOR to produce GOR totals • Calculate an HA distribution (excl. high weights) - Subtract high weights from IPS HA totals to produce ‘HA distribution’ for each GOR • Apply ‘HA distribution’ to GOR total to produce new HA totals

32. International Migration Methodology 2 • The HA totals are then smoothed over 3 years: 3yr HA total x GOR total (current year) 3yr GOR total • Split by LA within HA: • Inflows: using Census distribution: usual address 1 year ago (all immigrants) • Outflows: using previous year’s population distribution • Apply National age-sex distribution (IPS)

33. International MigrationChallenges • Overlap with Armed Forces • Particular areas difficult to estimate.Outflows for these areas may result in an underestimation. • First Onward Moves: • Links between Internal and International Migration. May be missing vital data. • Sample Variation • Intentions vs. Actuality

34. Visitor and Migrant Switchers Definitions • Migrant Switchers (Subtracted): • Persons who state the intention (in the IPS) to stay in the destination country for more than a year but who actually leave sooner. • Visitor Switchers (Added): • Persons who enter (or leave) the UK as visitors, but subsequently extend their visit to 12 months or longer. • Includes both EEA and non-EEA people

35. School Boarders Sources • England - DfES (Department for Education and Skills, Pupil Statistics Unit) • Wales - WAG (Welsh Assembly Government, Statistical Directorate) • Collected on annual returns from schools. • Includes public and state schools.

36. School BoardersMethodology • Compare previous year figures with current year to derive annual change figure. • Add annual change to population base. • Schools allocated to LA based on postcode. • Information on boarders collected at SYOA, 7 to 18.

37. School BoardersChallenges • Data Quality • Data on 81,500 boarders in 860 schools received • Final Total 82,200 boarders from 920 schools • Missing Schools (forms not returned) • Schools incorrectly record day-pupils as boarders • Is Definition of “boarder” suitable? • In recent times more schools have required local GP registration - hence boarders may be captured through standard internal migration.

38. PrisonsSources • Home Office

39. PrisonsMethodology • Compare previous year figures with current year to derive annual change figure. • Add annual change to population base. • Prisons allocated to LA based on postcode. • Information on prisoners collected at SYOA, 14 to 90+

40. Prisons Challenges • Quality of raw data • Prisons codes can be incorrect in source • Combining of Prison medical service into NHS.

41. Home Armed Forces (HAF)Methodology 1 • Mid-year population estimates include all people usually resident in England & Wales but NOT HM Forces (or their dependents) stationed overseas • Data on HM Forces (incl. Gurkhas) received from Defence Analytical Services Agency (DASA)

42. Home Armed ForcesMethodology 2 Each year • Remove previous year HAF resident in E&W • Add back in all previous year UKAF from E&W • Add previous year E&W service families overseas Age on, then • Remove current year UKAF from E&W • Add in HAF resident in E&W • Remove E&W service families overseas

43. Home Armed Forces Methodology 3: UKAF from E&W • Receive UKAF by age (16-59) & sex • Apply Census ratio to estimate those from England, and from Wales

44. Home Armed Forces Methodology 4:HAF resident in E&W 1 • Receive HAF by sex by base LA • take average of Oct, Jan, Apr & July figures • Re-distribute ‘Whitehall Warriors’ (These are armed forces personnel based in London doing ‘desk jobs’) • Remove a percentage (based on 1998 data) from Westminister • Re-distribute across London using Census data

45. Home Armed Forces Methodology 5:HAF resident in E&W 2 • Add in Gurkhas • Receive Gurkhas by unit (all male) • Assign to base LA • Use base-to-residence matrix from the Census assign to LA of residence (by sex) • Base county to resident LA matrix • For each county we only include LAs with more than 30 males or 10 females resident except where there is a small base

46. Home Armed Forces Methodology 6:HAF resident in E&W 3 • Apply age distribution by sex by LA from the Census • Constrain sub-national age-sex totals to national age-sex totals provided by DASA

47. Home Armed ForcesMethodology 7:Service Children Overseas 1 Receive UKAF married men overseas by force • Apply scaling factors (based on 1998 data) by force to estimate children overseas • Apply Census ratio to estimate those from England, and from Wales • Assume equal number of male and female children • Apply age distribution

48. Home Armed ForcesMethodology 8:Service Children Overseas 2 Age Distribution • Receive estimate of number of children in families overseas receiving child benefit by age • Apply ‘boarding school factors’ (based on Census) to remove those still at school in E&W (ages 11-14)

49. Home Armed ForcesMethodology 9:Service Wives Overseas Receive UKAF married men overseas by force • Apply proportions (based on 1998 data) by force to estimate wives overseas • Apply Census ratio to estimate those from England, and from Wales • Assume wives have same age distribution as husbands and apply age distribution for UKAF married men overseas.

50. Home Armed ForcesSources 1 • DASA (Defence Analytical Services Agency) • UKAF by age (16-55+) and sex • HAF by age and sex and base LA • Gurkhas by unit • UKAF married men overseas by age and sex • Her Majesty’s Revenue and Customs (HMRC) • Children in families overseas receiving child benefit by age (based on 5% sample)