Population Estimates Jonathan Swan, ONS

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Population Estimates Jonathan Swan, ONS
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Mid-year population estimates

• The ONS mid-year population estimates
• At national level for England, Wales
• At subnational level, for regions and local
  areas including government office regions
  (GORs), strategic health authorities (SHAs) and
  local authorities (LAs)
• By single year of age (to 90) and sex
• Annually one year in arrears (mid-2005 were
  published on 24 August 2006)
• Estimate the population as at 30 June

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Other Products

• Primary care organisation (PCO) estimates
• Marital status estimates
• Household population estimates (experimental)
• Quarterly population estimate (experimental)
• Small area population estimates (experimental)
• Ethnic population estimates (experimental)
• National population projections
• Subnational population projections
• Currently looking at new population definitions,
  such as daytime population, weekday population.

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Key uses of 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

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Population Estimates - Methods

• 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.

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Methods (contd) Static Populations

• These are sub-populations that dont 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)

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Cohort Component Method - National

• Population
• Base (aged on)
• Births - Deaths
• Net Internal migration (cross-border flows)
• Change in home armed forces in country
• (UKAF, HAF, Overseas families)
• Change in foreign armed forces in country
• (FAF, FAF dependents)
• Net International migration
• (IPS, VS, AS, MS, Eire)

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Cohort Component Method - Subnational

• Population
• Base (aged on) Births - Deaths
• Net Internal migration
• Change in school boarders
• Change in prisoners
• Change in home armed forces (HAF only)
• Change in foreign armed forces (FAF, FAF dep)
• Net International migration
• (IPS, VS, AS, MS, Eire)
• Boundary adjustment
• Reconciliation Adjustment

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Data Sources

• Census - base and used for distributions
• Registration data - births, deaths
• NHSCR and GP Patient Registers - internal
  migration
• International Passenger Survey international
  migration
• Home Office - Asylum Seeker data
• DASA - Armed Forces
• US Army, Navy, and Air Force - Foreign Armed
  Forces
• DfES/ WAG Boarding Schools
• Home Office - Prisoners

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Internal Migration - Definitions

• 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

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Internal Migration - 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

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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

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International Migration Overview 2
Total International Migration
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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

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Proportion of inflows by UK countries/ English
GORs
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IPS Central Tendency in the North East
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Description of improved methodology (UK to
GOR/Country)

• Calibration methodology developed for using LFS
  distributions to allocate IPS in-migrants at
  GOR/country level

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Description of improved methodology (new
intermediate geography)

• Group positive central tendency LAs with
  surrounding LAs
• Not all LAs have positive central tendency or
  surround one that does
• Group remaining LAs to achieve a minimum number
  of contacts
• A new migration geography created for all LAs
  in England Wales outside London

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IPS Intermediate Geography for London
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Description of improved methodology (new
intermediate geography - London)

• Country of birth used as basis for grouping
• Cluster analysis used to group
• Aim of grouping together areas which share
  similar stocks of people born in different parts
  of the world
• Students treated separately
• Distributed directly from GOR to LA using Census
  data on usual address one year ago

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Description of improved methodology (age-sex
distribution at LA level)

• Currently a national IPS age-sex distribution is
  applied at LA level
• However, the age distributions for immigrants
  vary between LAs
• Improved methodology
• Cluster LAs together sharing similar age
  distributions
• The centroid (average) age distribution is
  applied to each LA in that cluster
• Six age distribution types identified separately
  for males and females

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Six cluster centroid age distributions produced
for female immigrants
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New International Out Migrant Model
Published IPS national total
3 Year IPS average to apportion GOR
New Intermediate Geography (NIG)
Propensity to Migrate model to apportion NIGs
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Examples of New Intermediate Geography North
East and South East
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Propensity to Migrate Model

• Uses linear regression to predict the number of
  migrants per head of population.
• Uses entry selection method to select from 111
  socio, economic, and demographic variables.
• Used to apportion from New Intermediate Geography
  to local authority level.
• Significant improvement in model fit
• R2 increases from 42 to 89.5

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Visitor and Migrant Switchers

• 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.

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Task Force

• Placeholder

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Future Work Programme

• Placeholder

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Short Term Migrants Slide under development

• Definition of Long-term
• Definitions of Short Term
• Consultation

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Integrated Population Statistics System

• This is essentially a population register
• Linking various administrative and other data
  sources
• Removing the need for a Census, or something as
  extensive as the Census
• Dependent on initiatives such as ID cards, and
  removing some of the restrictions on sharing data
  across government

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How to have an Impact (slide under development)

• Write to us pop.info_at_ons.gsi.gov.uk
• Raise your issues through LGA to Discuss at the
  Central Local information Partnership (CLiP)
  Population Sub Group
• Attend the May Seminars
• Respond to Consultations
• Short-term Migrants
• Invite us to Groups and contribute
• Publish Research (Population Trends, BSPS
  Conferences etc.)

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For further information

• See
• Making a Population Estimate
• Contact Population Estimates Unit
• tel [phone]
• email Pop.info_at_ons.gov.uk
• Visit the NS website
• www.statistics.gov.uk/popest and
• www.statistics.gov.uk/imps