Geography and Geographical Analysis using the ONS

Longitudinal Study

Christopher Marshall

&

Julian Buxton

CeLSIUS

• 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 of using geographical data in the LS.

• The Role of CeLSIUS (Centre for Longitudinal Study Information and User Support).

Aims of the Presentation

The ONS Longitudinal Study

• Census data for individuals with one of four birthdates enumerated at the 1971 Census (c. 1% of population)

• Maintained through addition of immigrants and new births 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.

| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |1971 1976 1981 1986 1991 1996 2001 2006 2011

Birth ofChild

Birth ofChild Census Emigration Re-entry

Death ofSpouse Census Cancer Death

Study Structure

1971

Original sample: 530,000; selected from 1971 Census

1981

536,000 sample members found at 1981 Census

1991

543,000 sample members found at 1991 Census

2001

545,894sample members found at 2001 Census

Plus members of household

Plus members of household

Plus members of household

Plus members of household

Entrants New Births 214,000 Immigrants 107,000

Deaths 189,000 Embarkations 30,000

Births to sample women 201,000Events 1971 - 2001 Widow(er)hoods 66,000

Cancer registrations 70,000

1. Census. High N. 2. Linking 3. Non-members 4. Entrance & Termination 5. Events

Geographical Location of LS Members

From Census Information• Based on Address of Usual Residence on

Census Day

• Visitors flagged prior to 2001 and usually excluded from studies

• Fully coded to the Administrative boundaries and also to Health boundaries (e.g. Regional Health Authority)

Main Time Points Available

1. 1970 from address 1 year ago 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 theory)

Census 1971 1981 1991 2001

Region SR 1971 & SR 1974

SR 1974 SR 1974 GOR 2001

County 1971 & 1974

1974 1974 2001 & 2003

County District

1971 & 1974

1974 1974 2001 & 2003

Ward 1971 & 1974

1974 1974 2001 & 2003

Lower Levels

Grid Reference

Enumeration District

Enumeration District & Postcode

GR, PC, ED & Output Areas

LS Geography (England & Wales) 1971 - 2005

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

1971 - Living in NE

Social Class: Skilled Non-Manual

Tenure: Social Housing

2001 - Living in SE

Social Class: Managerial

Tenure: Owner Occupier

Social and Geographical Mobility

Geographical Migration Patterns

South East 1981

South West 2001

North East1971

Use of existing definitions - Geographical

• Continuity for 30 years at 1974 geography despite changing boundaries.

• Standard Region / Government Office Region

• 2001 can be mapped to preceding years and look-up 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)

Create new definitions - Geographical

•Urban – Rural

•Travel to Work

•Craig – 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 table with a valid geographical reference code (e.g. Ward, County District) attached.

Air pollution indicators

Average rainfall in 10 years

Ecological Deprivation indices

Create new geographies

It could be that for your specific purpose the Geographies within the LS are inappropriate.

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 into two or three separate areas not wholly based on counties.

Look at specific areas

The purpose of your analysis is to look only at a specific area of the country and compare 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 at Ward level or below would require aggregation of results, while at county district level, outputs do not usually require aggregation.

Strengths of geographical data in the LS

1. Consistency over time – 1971, 1981, 1991 all 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.

3. 30 years of continuous follow-up of individuals

4. 9 Time points (1966 – 2001)

5. Consistency of geography through this time period.

Strengths of geographical data in the LS

6. Flexibility of study design

7. Individual and Area data

8. Can add data using geographical identifiers (e.g. Carstairs deciles)

9. High level of detail available for later data.

Strengths 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 lay traps for the unwary.

Weaknesses of geographical data in the LS

ScotlandMembers in 1971 found with a Scottish NHS number were incorporated into the LS.

Events to LS members (e.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 the LS. Earlier data remain within the 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 to users), and for publication 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:

Occupation Country of birth

Industry Ethnicity

Cause of Death Higher education levels

Sub regional geographical fields

Examples of Using LS Geography 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 present at 1991 & 2001, Males: 55-65 in 1991 & Females 50-60 in 1991

All resident within Greater London in 1991 – from county code 1991

1. Do people move out of London when they retire?

Source: ONS Longitudinal Study

GOR of residence in 2001 by Sex for those living in London in 1991

GOR of residence2001 Male Female Total %

North 12 9 21 0.38York&Humb 11 10 21 0.38E Mids 24 31 55 0.98W Mids 9 11 20 0.36E of Eng 130 130 260 4.64SE 147 192 339 6.06SW & Wales 69 67 136 2.43London-not moved 1,755 2,144 3,899 69.65London-moved 369 478 847 15.13

Total 2,526 3,072 5,598 100.00

Sex

2. Has the population distribution between Urban and Rural areas changed between 1991 and 2001?

Main Study Population:

LS members present at 1991 & 2001Age 16 - 55 in 1991

Report: resident in Urban / Rural Ward classification in 1991 and in 2001 using 1974 boundaries.

Research Question:

2. Distribution of Urban / Rural residency between 1991 and

2001.

Simple Ruralclassification 1991 < 400 / sq km >400 / sq km Total(people per sq km) (Rural) (Urban)

< 400 / sq km rural 32,985 13,606 46,591>400 / sq km Urban 17,093 181,639 198,732

Total 50,078 195,245 245,323

Simple Ruralclassification 2001

Source: ONS Longitudinal Study

Area of residence 1991 v Area of residence 2001

The Role of CeLSIUS (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:

•Socio-economic indicators

•LS Outputs

•Households and families

•Defining a study population

•Ethnicity

•Geography – NEW just released

www.celsius.lshtm.ac.uk

A Free service for UK academic users

General enquiries:celsius@lshtm.ac.uk020 7299 4634

Emily Grundy Andy Sloggett Lynda Clarke Julian BuxtonChristopher Marshall Jo Tomlinson