Population Projections by Ethnic Group

Pete Large

ONS

pete.large@ons.gov.uk

Population Projections by Ethnic Group

• Estimates and projections by ethnic group• Deriving the ethnic dimension • Implementation and output• Ethnicity in the 2011 Census

Population Projections

• National (GAD), 25/40/70 years• Sub-National (ONS), 25 years, LADs

• Ethnic (ONS), 10 years, LADs ?, 16-way classification

Population Projections by Ethnic Group

• Feasibility study in 2002• ‘Spin off’ of Ethnic Estimates work• To cover England (and subdivisions) only• Methodology to be QA’d• Release as Experimental Statistics possible in

December 2005 (subject to review)

Projection Method

• Cohort Component Method

Yn+1 = Yn + Bn+1 – Dn+1 + Sn+1 + Nn+1

• Constrain to Sub-National Projections

Difficulties of Ethnic Projections

• Lack of key data with ethnic dimension:– Need to use proxies– Use data from different sources

• Inconsistent classifications

• Small groups

Size of Ethnic Groups

As a percentage of the population of England

• White: British = 87.0%• Next largest: White: Other = 2.7%• 10 groups each have less than 1.0%

Source: Table KS06, 2001 Census, ONS, Crown Copyright

Cumulative Proportion of non-White: British (LADs in England)

0

0.25

0.5

0.75

1

1 16 31 46 61 76 91 106 121 136 151 166 181 196 211 226 241 256 271 286 301 316 331 346

Cumulative proportion

Number of LADs

Source: KS06, 2001 Census, ONS, Crown Copyright

The Ethnic Dimension: Fertility

Yn+1 = Yn + Bn+1 – Dn+1 + Sn+1 + Nn+1

Fertility

• Need relative level and shape of age-fertility curves

• Possible sources: Birth Register (COB), LFS, Hospital Episode Statistics, Longitudinal Study, 2001 Census

Population of England and Wales:Percentages born in UK

• 91% of all people born in UK• 41% of non White: British born in UK

• White British: 98%• Other White 20%• Asian groups 47%• Black groups 49%• Other groups 34%

Note: Data is for England and Wales. Source S102, 2001 Census, ONS, Crown Copyright

Fertility

• 2001 Census provides numbers of 0 year olds to mothers of each ethnic group by SYOA

• Implied ‘relative fertility rate’ applied to Sub-National Projections (SNP) curves

• Project changes in relative fertility ?

• Total births for each age/area constrained to SNP

Illustrative Fertility Profiles

0.000

0.020

0.040

0.060

0.080

0.100

0.120

0.140

15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44

All groups

Black: African

Note: Data illustrative only

Illustrative Calculation of Fertility Rate

CensusAge-Specific Fertility Rates (Age 29, England)All groups 0.094Black: African 0.124Relative ASFR = 0.124 / 0.094 = 1.314

Sub-National ProjectionsAge-Specific Fertility Rate (Age 29, LAD x) = 0.1

Estimated ASFR (Age 29, LAD x, Black African)= 1.314 x 0.1 = 0.131

Married Women in Inter-Ethnic Marriages

White: British 3%

White: Irish 63%

Mixed: White and Asian

82%

Asian: Indian 9%

Black: Black Caribbean

25%

Black: Other 66%

Chinese 29%

Source: Focus on Ethnicity & Identity, ONS, at www.statistics.gov.uk/cci/nugget.asp?id=1090, Crown Copyright

Allocation of Births to Ethnic Group

• 2001 Census provides ethnicity of mother by ethnicity of child for SYOA 0-9

• Assumed different patterns for London and the rest of England

• Linear projection from 1997-2001 to 2013 ?

Getting the probabilities wrong …

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

1

7

13

19

25

31

37

43

49

55

61

67

73

79

85

Ag

e

(000s)Note: Illustrative data only

The Ethnic Dimension: Mortality

Yn+1 = Yn + Bn+1 – Dn+1 + Sn+1 + Nn+1

Mortality

• Unlikely to be key factor in estimates of population by ethnic group

• Country of birth as proxy ?• Confounded with area effects

• Constrain to SNP – mortality rates as an output

‘Ethnic Switching’

Yn+1 = Yn + Bn+1 – Dn+1 + Sn+1 + Nn+1

Switching between Ethnic Group

• Using 1991/2001 Census data from Longitudinal Study

• BUT– Imputation– Response by others in household– Change in ethnic classification

Unable to reliably estimate switching effect

The Ethnic Dimension: Migration

Yn+1 = Yn + Bn+1 – Dn+1 + Sn+1 + Nn+1

Migration

• Domestic Migration (within England)

• Migration to/from rest of UK

• International Migration– IPS/VS– Asylum Seekers– Irish

Domestic Migration

• Need to establish:– Relative propensity to migrate– Likely destination

• Relative propensity to migrate: Census data on age-migration profiles

• Likely destination:– Age effect– Ethnicity effect

Each flow A->B constrained to Sub-National Projection

Migration from Rest of UK

• Rest of UK assumed exogenous

• In-migration decomposed using 2001 Census ethnic proportions for in-migrants

• Investigate possibility of ‘ethnic effects’

• Constrain to Sub-National Projections for each part of ROUK/area within England

Migration to Rest of UK

• Similar methodology to domestic migration• Takes account of age structure and ethnic effects

for each area

• Some aggregation of groups required for Scottish data

• Ethnic composition of flow to Northern Ireland assumed same as inflow

IPS/VS Migration: Outflow

• IPS data on COB/Country of Next Residence• Census data on COB/Ethnicity• Care needed for some small flows

IPS Migration: Outflow

Component Cumulative % of migrants

British citizens travelling to EU/USA/Australia/Canada/NZ/South Africa

43

EU citizens travelling to the EU

55

Commonwealth citizens travelling to Canada/SA/Australia/NZ

68

… …

IPS/VS Migration: Inflow

Option 1:• Adjust 2001 Census counts of migrants for Asylum

Seekers and Irish flows in each area• Apply derived rates to Sub-National Projections

flows

Option 2:• Do the same as with outflow (use COB to derive

ethnicity from Census data).

Asylum Seekers

• Take account of both inflow and outflow• Home Office data on nationality of asylum seekers

over past 5 years• Census data on COB/Ethnicity• White: British set to zero• Apply rates to Sub-National Projections

This component subject to substantial variation

Irish Flows

Option 1• Assume ethnic composition is same as flows

to/from Northern Ireland

Option 2• Use ethnic composition of inflows from Ireland

measured in the Census (and assume same applies to outflows)

The Ethnic Dimension: Starting Population

Yn+1 = Yn + Bn+1 – Dn+1 + Sn+1 + Nn+1

Starting Population

• Apply projection method to 2001 Census data to mid-years 2001-2003

• Allow for special populations of Armed Forces, school boarders and prisoners

(Aim to be consistent with Mid-Year Estimates)

Variability of Projections

• Projections NOT Forecasts• Constraining totals given by National/Sub-National

Projections• Statistical error in estimating parameters• Correspondence between alternative plausible

methodologies

Implementation and Output

• Projection/estimates systems written in SAS

• System runs for LADs and 16-way ethnicity (any aggregation done at end)

• Output likely to follow Mid-Year Estimates/Sub-National Projections

– England: SYOA to 85 by ethnicity– LADs (?): Quinary age to 85 by ethnicity

• Results expected to be available in Excel/CSV format on website

Census 2011 consultation - Ethnicity, Identity, Language and Religion

• Consultation on topics runs 16 May to 5 Aug 2005• Aiming to establish users’ data requirements and

build on ONS’s current understanding– Topics which have a clear case for inclusion:

• Ethnicity, religion and national identity• Country of birth• Welsh/Irish/Gaelic proficiency in Wales/Northern

Ireland/Scotland

– Topics which need further investigation:• Nationality/citizenship

– Topics which have insufficient evidence of user need:• Country of parents’ birth• English language proficiency

Census 2011 Consultation web page

• For more information on the consultation, including how to respond:

http://www.statistics.gov.uk/about/consultations/2011Census.asp

Population Projections by Ethnic Group

Questions ?