Geography and Geographical Analysis
using the ONS Longitudinal Study
Christopher Marshall
&
Julian Buxton
CeLSIUS
Aims of the Presentation
• What is the ONS LS and what data does it contain?
•
What geographical information is in the LS and at what
level?
•
What does this allow us to do?
•
The strengths and weaknesses of using geographical data in
the LS.
•
Examples
a p es oof us
using
g geog
geographical
ap ca data in tthee LS.
S.
•
The Role of CeLSIUS (Centre for Longitudinal Study
Information and User Support).
The ONS Longitudinal Study
• Census data for individuals with one of four birthdates
enumerated at the 1971 Census (c. 1% of population)
• Maintained
M i t i d th
through
h addition
dditi off iimmigrants
i
t and
d new bi
births
th
with LS birth date
• Information from later censuses (1981, 91 & 2001) added
and linked to that already there.
• Event data including deaths of LS members, cancer
registrations, death of spouse, births to female members,
and now, under test, the Claimant Count Cohort.
Birth
of
Child
Birth
of
Child Census
Emigration
Death of
Re-entry Spouse
Census
Cancer
Death
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
1971
1976
1981
1986
1991
1996
2001
2006
2011
Study Structure
Entrants
New Births
1971
214,000
Immigrants
107,000
1981
1991
2001
Original
sample:
530,000;
selected from
1971 Census
536,000
sample
members
found at 1981
Census
543,000
sample
members
found at 1991
Census
545,894
sample
members
found at 2001
Census
Plus members
of household
Plus members
of household
Plus members
of household
Plus members
of household
Births to sample women 201
201,000
000
Widow(er)hoods
66,000
Cancer registrations
70,000
Events 1971 - 2001
Deaths
189,000
1. Census. High N.
Embarkations
2. Linking
3. Non-members
30,000
4. Entrance & Termination
5. Events
G
Geographical
hi l Location
L
ti off LS Members
M b
From Census Information
• Based on Address of Usual Residence on
C
Census
D
Day
• Visitors flagged prior to 2001 and usually
excluded from studies
• Fully coded to the Administrative boundaries
and also to Health boundaries (e
(e.g.
g Regional
Health Authority)
Main Time Points Available
1. 1970 from address 1 y
year ago
g in 1971
2. Census day 1971 (25th/26th April)
3. 1980 from address 1 year ago in 1981
4. Census day 1981 (5th/6th April)
5. 1990 from address 1 year ago in 1991
6. Census day 1991 (21st/22nd April)
7. 2000 from address 1 year ago in 2001
8. Census day 2001 (29th/30th April)
9. Also possible: 1966 from address 5 years ago 1971
10 1939 (in
10.
(i theory)
h
)
LS Geography
G
h (England
(E l d & Wales)
W l ) 1971 - 2005
Census
1971
Region
SR 1971 &
SR 1974
County
1981
SR 1974
1991
2001
SR 1974
GOR 2001
1971 & 1974 1974
1974
2001 & 2003
County
District
Ward
1971 & 1974 1974
1974
2001 & 2003
1971 & 1974 1974
1974
2001 & 2003
Lower
Levels
Grid
Reference
Enumeration Enumeration GR,
GR PC,
PC ED
District
District &
& Output
Postcode
Areas
What does this allow us to do?
• Migration:
• Mobility – Geographical & Social Categories
•
Use existing definitions
•
Create new analytical definitions
•
Attach and analyse ecological data
•
Create new geographies
•
Analyse specific areas
S i l and
Social
dG
Geographical
hi l Mobility
M bilit
1971 - Living in NE
Social Class: Skilled Non-Manual
Tenure: Social Housing
2001 - Living in SE
Social Class: Managerial
Tenure: Owner Occupier
Geographical Migration Patterns
North East
1971
South East
1981
South West
2001
Use of existing definitions - Geographical
• Continuity for 30 years at 1974 geography
despite changing boundaries
boundaries.
• Standard Region / Government Office Region
• 2001 can be mapped to preceding years and lookup tables can bring earlier geographies forward
to 2001
• County and County Districts can be treated
similarly.
Use of existing definitions: Geographical (2)
• Administrative boundaries
• Environmental boundaries
• Ecological Deprivation Indices
• Area Classifications (Urban / Rural)
• Population densities
• Small area statistics (Aggregate level variables)
C
Create
t new d
definitions
fi iti
- Geographical
G
hi l
•Urban – Rural
•Travel to Work
•Craig
g – Webber
•Other valid divisions
Create new definitions: Socio-economic
•Social Class by Sex
•Social Class by Age Group
•Working Status – Age Group
•Social Class by Tenure
Attach ecological or social data
Any data can be attached to individual LS
members if it is produced in the form of a look-up
look up
table with a valid geographical reference code
(e.g. Ward, County District) attached.
Air pollution indicators
Average rainfall in 10 years
Ecological Deprivation indices
C
Create
new geographies
hi
It could be that for your specific purpose the
Geographies
g p
within the LS are inappropriate.
pp p
Define the geography you want based on LS wards
or county districts and this can be attached to LS
members and used for analysis.
e.g. We have regions but you want to divide each
i
into
two or three
h
separate areas not wholly
h ll based
b
d on
counties.
Look at specific areas
The purpose of your analysis is to look only at a
specific
p
area of the country
y and compare
p
it with one
or two others.
Depending on parameters chosen the analysis can
run into ‘disclosure control’ restrictions – keep the
analysis simple with a limited number of parameters.
Analysis
A
l i at Ward
W d llevell or below
b l
would
ld require
i
aggregation of results, while at county district level,
outputs
p
do not usually
y require
q
aggregation.
gg g
Strengths of geographical data in the LS
1 C
1.
Consistency
i t
over ti
time – 1971,
1971 1981
1981, 1991 all
ll
coded to same base (1974 geography). 2001
can be produced on the same base down to
county district level with confidence fairly
easily.
2. If necessary earlier data can be brought
forward to 2001 by the use of look-up tables.
Strengths of geographical data in the LS
3. 30 years of continuous follow-up of
individuals
4. 9 Time points (1966
(
– 2001))
5. Consistency of geography through this time
period.
i d
Strengths of geographical data in the LS
6. Flexibility of study design
7. Individual and Area data
8. Can add data using
gg
geographical
g p
identifiers
(e.g. Carstairs deciles)
9. High level of detail available for later data.
Weaknesses of geographical data in the LS
1. While County and County District Codes
have remained fairly consistent the Ward
codes needed to attach additional data have
changed significantly over time.
2. Data are for England and Wales only
3. Members who move to Scotland classed as
embarkations (migrants)
Weaknesses of geographical data in the LS
4. Data codings and data detail not consistent.
5. It is not possible to ‘back transfer’ all
geographies.
6. Ward code history – many changes and
manipulations
i l i
lay
l traps for
f the
h unwary.
Scotland
Members
M
b
in
i 1971 found
f
d with
ith a Scottish
S tti h NHS
number were incorporated into the LS.
Events to LS members (e
(e.g.
g deaths) that occur
in Scotland are traced and do get linked to LS
members.
LS members who migrate to Scotland are
treated as Emigrants and this is recorded in
th LS
the
LS. E
Earlier
li d
data
t remain
i within
ithi the
th LS.
LS
Disclosure Control Rules
Researchers should design their projects such
that it would never be possible to identify an
individual from the output data generated
(Population uniques).
Output cell counts of 1 or 2 are considered
potentially disclosive (although most 2s will be
released
l
d tto users),
) and
d ffor publication
bli ti purposes
some aggregation of data would be required.
Exposure times for single events are a
considered a risk and have to be disguised.
Disclosure Control Rules
Tables containing data with a mix of any of the
following types of variable will be examined
more scrupulously:
l
l
Occupation
Country of birth
Industry
Ethnicity
Cause of Death
Higher education levels
Sub regional geographical fields
Examples
p
of Using
g LS Geography
g p y
within a project
1. Do people move out of London when they
retire?
2. Have people moved from Urban to Rural areas
between 1991 and 2001?
Research Question:
1. Do people move out of London when they retire?
Main Study Population:
LS members
b
presentt att 1991 & 2001
2001, M
Males:
l
55
55-65
65 iin
1991 & Females 50-60 in 1991
All resident within Greater London in 1991 – from
county code 1991
1 D
1.
Do people
l move outt off L
London
d when
h th
they retire?
ti ?
GOR of residence in 2001 by Sex for those living in London in 1991
GOR of residence
2001
Sex
Male
Female
Total
%
North
York&Humb
E Mids
W Mids
E of Eng
SE
SW & Wales
London-not moved
London-moved
12
11
24
9
130
147
69
1,755
369
9
10
31
11
130
192
67
2,144
478
21
21
55
20
260
339
136
3,899
847
0.38
0.38
0.98
0.36
4.64
6.06
2.43
69.65
15.13
Total
2,526
3,072
5,598
100.00
Source: ONS Longitudinal Study
Research Question:
2. Has the population distribution between
Urban and Rural areas changed
between 1991 and 2001?
Main Study Population:
LS members present at 1991 & 2001
Age 16 - 55 in 1991
Report: resident in Urban / Rural Ward
classification in 1991 and in 2001 using 1974
boundaries.
2 Di
2.
Distribution
t ib ti off Urban
U b / Rural
R
l residency
id
between 1991 and 2001.
Area of residence 1991 v Area of residence 2001
Simple Rural
classification 2001
< 400 / sq km >400 / sq km Total
(Rural)
(Urban)
Simple Rural
classification 1991
(people per sq km)
< 400 / sq km rural
q km Urban
>400 / sq
32,985
17,093
,
13,606
181,639
,
46,591
198,732
,
Total
50,078
195,245
245,323
Source: ONS Longitudinal Study
Th R
The
Role
l off C
CeLSIUS
LSIUS
(Centre for Longitudinal Study Information and User Support)
An interface between academics and the Office for
National Statistics.
Provide - through our Web site - information on:
• The structure of the ONS LS.
• How to decide if it is for you.
• Training modules to assist your understanding of the
data and how it can be manipulated.
• All the documents needed to apply for permission to
use the ONS LS and access to the LS datasets.
The CeLSIUS training modules
modules:
•Socio-economic indicators
•LS Outputs
•Households and families
•Defining
D fi i a study
d population
l i
•Ethnicity
•Geography – NEW just released
www.celsius.lshtm.ac.uk
A Free service for UK academic users
General enquiries:
celsius@lshtm.ac.uk
020 7299 4634
Emily Grundy
Lynda Clarke
Christopher Marshall
Andy Sloggett
Julian Buxton
Jo Tomlinson