The micro-geography of UK demographic change 1991-2001

Paul NormanSchool of Geography, University of Leeds

Understanding Population Trends & ProcessesESRC RES-163-25-0012 for 2005-07 @ 40%

Aims

1. Quantify and map changes in population size and social characteristics which occurred in UK’s small geographical areas between the 1991 and 2001 Censuses

2. Calculate components of demographic change to understand the relative contributions of natural change and migration

3. Calculate deprivation indexes to identify areas becoming differently deprived over time

4. Inform on locations where the population is ageing or more transient, along with small area trends in unemployment, health and deprivation

Small area geography of reporting: wards & equivalents

Calculating population change1991 and 2001 ‘ward’ populations not comparable:

• Boundary changes

• Differences in 1991 & 2001 Census population definition (students)

To estimate a 1991 base population, need to:

• Adjust populations to mid-year & to a consistent geography

• Allow for changed view of level of 1991 Census undercount

Collaboration with Ludi Simpson and Albert Sabater at CCSR

• Examples here using Birmingham

1991 to 2001 boundary changeAdjust 1991 data to the 2001 boundaries

4 0 4 8 Kilometers

2001 Ward Boundaries1991 Ward Boundaries

N

1991 to 2001 boundary changeApportion data using weighted postcode distribution

District boundary 1991

District boundary 2001

Apportion 1991 ward data

Uffdown ward 1991

Waseley ward 1991 Method:

• Simpson (2002) &• Norman et al. (2003)

Longridge ward

Estimating official 1991 populations

1990s viewpoint (original)

Official Mid-Year Estimates (MYEs) for 1991 districts

Based on 1991 Census ‘usual residents’ with adjustments for:

• Student term-time adjustment

• Demographic change between Census day & mid-1991

• Armed forces postings adjustment

Census under-enumeration (c. 1.2 million people)

• ‘Non-response’ adjustments (by age) ‘Other’ adjustments

Official MYEs for 1991 districts

Populations

Adjustments

Estimating with Confidence (EwC) 1991 small area MYEs

1990s viewpoint (original)

EwC estimated 1991 small area mid-year populations as:

Census ‘usual residents’ with allowances for:

• Student term-time adjustment

• Demographic change between census and mid-1991

• Modification adjustment (table consistency)

• Armed forces adjustment

• Residual non-response (by age)

An area-specific application of official district level adjustments

EwC 1991 adjustments (original)

Non-response adjustments

Other adjustments

EwC 1991 adjustments (original)

After 2001 Census 1991 MYEs revised

Adjustments• Non-response revised downwards• Other adjustments remain the same

Populations

Revising 1991 EwC small area MYEsPost-2001 viewpoint (revised)

For sub-district areas, by age & sex:

• Adjust EwC populations & adjustments to allow for 1991 to 2001 boundary changes

• Distribute original EwC non-response adjustments revisions on area-specific basis scaled by difference between 1991 MYEs district pre- & post-revisions

• No revisions made to the ‘other’ (student, armed forces, timing or modification) adjustments, which are still assumed to apply

• Ensure small area data sum to the 1991 revised district MYEs

Revising the non-response adjustmentFor males aged 20-24 in Birmingham

Assessing EwC revised

Total male non-response• Difference in estimates related to size of original non-response

Total male population• Different downward revisions

Assessing EwC revised Relationships should be maintained

Implications of EwC revisions 1991 to 2001 population change

Original cf. Revised …Net population change:• Growing wards grow more• Contracting wards contract less

Implications of EwC revisions

1991-2001 net malepopulation change

EwC Revised

1991-2001 net malepopulation change

EwC Original

4 0 4 8 KilometersN

Change (Original)-2500 to -1500-1500 to -50 -50 to +50 +50 to 500 500 to 1500

Change (Revised)-2500 to -1500-1500 to -50 -50 to +50 +50 to 500 500 to 1500

Implications of EwC revisions Different age-sex structure of ward populations

District adjustments• Non-response revised downwards• Other adjustments remain the same

Ward adjustments• Reduction in number of males by age• In proportion to size of original non-response

Implications of EwC revisions EwC Original & Revised used as a denominator:

Male unemployment

Male (<65) SMRs

Extras about this work

Geographical data conversions are 1991 EDs to 2001 OAs

• Improved geographical detail & aggregation versatility

Revisions to EwC by quinary age-group

• OA 1991 populations to be estimated by single year of age to 90+

• IPF using extra information on 0s, late teens and 80-89 & 90+

Albert Sabater will extend these estimates by ethnic group

Rest of UPTAP project to follow