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Population Estimates
Jonathan Swan, ONS
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
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.
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
Population Estimates - Methods
● Cohort component method:
Pt = Pt-1 + Bt - Dt + It
Population = Base (aged on) + Births - Deaths +
net Migration
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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”.
Methods (contd) – 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)
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)
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
Data Sources
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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
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
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
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
International Migration – Overview 2
Irish Flows
Asylum Seeker Adjustment
Visitor Switchers
IPS Migrants
Migrant Switchers
Total
International
Migration
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’
Proportion of inflows by UK countries/
English GORs
N. Ireland
Scotland
Wales
South West
South East
London
East
West Midlands
East Midlands
Yorks & Humb
North West
North East
0%
10%
20%
IPS
30%
LFS
40%
CENSUS
50%
IPS Central Tendency in the North East
Proportion of all Immigrants to LAs in North East
Proportion of All Immigrants
0.60
IPS
0.50
CENSUS
0.40
0.30
0.20
0.10
0.00
LA
Description of improved methodology
(UK to GOR/Country)
● Calibration methodology developed for using
LFS distributions to allocate IPS in-migrants at
GOR/country level
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
IPS Intermediate Geography for London
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
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
Six cluster centroid age distributions produced
for female immigrants
New International Out Migrant Model
National: England and Wales
Wales
New Intermediate
Geography (NIG)
North East
NEI1
Published IPS
national total
North West
NEI2
High weights
adjustment
Newcastle-u-T
Gateshead
Wansbeck
Published IPS
Wales/GOR
3 Year IPS
average to
apportion GOR
Propensity to
Migrate model to
apportion NIGs
Examples of New Intermediate Geography:
North East and South East
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%
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.
Task Force
● Placeholder
Future Work Programme
● Placeholder
Short Term Migrants – Slide under
development
● Definition of Long-term
● Definitions of Short Term
● Consultation
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
How to have an Impact (slide under
development)
● Write to us: [email protected]
● 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.)
For further information:
See:
Making a Population Estimate
Contact Population Estimates Unit :
tel: 01329 813318
email: [email protected]
Visit the NS website:
www.statistics.gov.uk/popest and
www.statistics.gov.uk/imps