Update 06-2016
Ethnic Group Population Projections - Extension To
17 Ethnic Groups
November 2016
Summary
Up to 2015 (the 2014 Round of projections) the GLA have produced Ethnic Group Population Projections
on the basis of ten aggregated ethnic groups. For the upcoming ethnic projections to be published in 2016
the ethnic model has been extended to seventeen ethnic groups. The seventeen groups are the eighteen
ONS ethnic groups used in the 2011 Census, with the exception that the White Gypsy or Irish Traveller
group has been aggregated into the Other White group as it is too small to model on its own (see Appendix
1 for definitions).
This Update describes the outcome of extending GLA Ethnic Group Population Projections from ten
aggregated ethnic groups to seventeen ethnic groups. To quantify the effect of the seventeen-group
approach on ethnic population outputs the seventeen group outputs were aggregated up to the preceding
ten groups so that outputs from the two approaches could be compared like-for-like.
The seventeen-group model was developed using 2011 Census-based ethnic input parameters for each of
the seventeen groups, and constrained to the 2014 round long-term migration trend borough variant which
was published in 2015. The ten-group population outputs aggregated from the seventeen-group model
were compared with corresponding ten-group outputs produced by the preceding ten-group model for each
projection year 2011 to 2041.
For Greater London the differences between the two model outputs in the overall population for each of the
ten aggregated ethnic groups were mostly within +/- 1 per cent over the projection period. The main
exceptions were the Chinese, Other, and Black Other aggregated ethnic groups where overall population
differences exceeded 1 per cent for most of the projection period, reaching -2.3 per cent, 2.7 per cent, and
7.0 per cent by 2041 respectively.
At borough level the differences between the two model outputs in the overall population for each of the
ten aggregated ethnic groups were mostly within +/- 5 per cent by projection year 2041.
These results are close enough to establish consistency between the new seventeen-group model and the
original ten-group model. Hence ethnic group population projections for the 2015 round long-term
migration and short-term migration variants have been produced for seventeen ethnic groups using the
seventeen-group model. They are described in Update 07-2016 2015 Round Ethnic Group Population
Projections1.
1
https://data.london.gov.uk/dataset/2015-round-ethnic-group-population-projections
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Background
Up to 2015 (the 2014 Round of projections) the Greater London Authority (GLA) have produced ethnic
group population projections on the basis of ten aggregated ethnic groups. That is to say, model ethnicspecific input parameters were derived at the ten-group level and ethnic populations were output for the
corresponding ten groups.
There were two reasons for this. Firstly, initial GLA ethnic group populations projections used ethnic-specific
data from the 1991 Census, in which the ethnicity question was limited to nine ethnic groups, with ONS
adding a tenth group (Other Asian) to published census outputs which was derived from the write-in
responses to the ethnicity question.
Secondly, after the 2001 Census, which provided sixteen categories to choose from in the ethnicity
question, one consideration was whether to maintain continuity with the 1991 Census outputs and GLA
ethnic projections based on them. In addition, due to the counts of some of the sixteen categories being
small it was considered necessary to use ethnic group aggregation in order to diminish the impact of
statistical disclosure control applied in the 2001 census borough-level ethnic outputs published by ONS or
commissioned from them. Hence ethnic model design and outputs were maintained at the ten-group level.
In the 2011 Census, which provided eighteen groups to choose from in the ethnicity question, whilst small
counts were still present in the published and commissioned ethnicity outputs these were noticeably
reduced in quantity due to the increased overall ethnic populations. Furthermore, the statistical disclosure
control applied by ONS to these outputs used a different methodology than for 2001 census outputs and it
is considered that this would reduce the impact of disclosure control on the GLA ethnic modelling process.
There is also increased interest from users in having projected ethnic populations available for all of the
2011 Census ethnic groups. Hence the GLA ethnic projection model has now been extended to seventeen
ethnic groups, these being the eighteen ONS ethnic groups used in the 2011 Census, with the exception
that the White Gypsy or Irish Traveller group has been aggregated into the Other White group as it is too
small to model on its own (see Appendix 1 for definitions).
The methodology used for the GLA ethnic seventeen-group model is similar to that used for the preceding
ten-group model, but with updating of ethnic births modelling parameters and redefining all 2011 Census
ethnic input parameters in terms of the seventeen groups. This methodology is described in Update 052016 Ethnic Group Population Projection Model Methodology2.
The required 2011 Census ethnic outputs have not all been available in time for previous ethnic projection
rounds, so following the 2011 Census the 2012, 2013, and 2014 rounds of GLA Ethnic Group Population
Projections were produced for ten aggregated ethnic groups. The 2015 round, published in 2016, is the first
in terms of seventeen ethnic groups.
A consequence of moving to seventeen-group ethnic outputs is that there is no ethnic back-series for years
before 2011. This is because preceding census information was not collected on a corresponding ethnic
group basis.
This Update describes the outcome of extending GLA Ethnic Group Population Projections from ten
Aggregated Ethnic Groups to seventeen Ethnic Groups. To quantify the effect of the seventeen-group
approach on ethnic population outputs the seventeen-group outputs were aggregated up to the preceding
ten groups so that outputs from the two approaches could be compared like-for-like. The ten-group ethnic
populations from the seventeen-group model and the ten-group model outputs were compared and
analysed in order to assess the validity of the seventeen-group model and outputs.
2
https://data.london.gov.uk/dataset/2015-round-ethnic-group-population-projections
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Validation of Population Projections by 17 Ethnic Groups
The only available method of assessing the seventeen-group model outputs for the 2014 round long-term
migration trend variant was to compare them with the published outputs from the preceding ten-group
model for the same variant. For this it was necessary to aggregate the seventeen-group outputs back up to
the ten aggregated ethnic groups using the relationships in Appendix 1.
For this comparison, the published outputs for the 2014 round long-term migration trend variant, produced
by the ten-group model, are referred to as “10AEG” outputs. The ten-group outputs produced by the
seventeen-group model and aggregated up to ten groups are referred to as “10from17”. These two outputs
are compared at Greater London level for the last projection year, 2041, in Table 1.
Table 1: Comparison of Seventeen-group Model with Ten-group Model:
10 Aggregated Ethnic Groups, 2014 round long-term migration trend variant,
Greater London, 2041
10from17 - 10AEG
Aggregated Ethnic Group
All Ethnicities
White
Black Caribbean
Black African
Black Other
Indian
Pakistani
Bangladeshi
Chinese
Other Asian
Other
BAME
10from17
10AEG
diff
%diff
10,276,400
5,391,700
356,500
766,000
559,600
825,600
370,900
330,800
178,000
805,200
692,200
4,884,700
10,276,400
5,437,400
351,400
772,900
522,800
823,000
373,500
331,900
182,200
807,200
674,000
4,838,900
0
-45,800
5,100
-6,900
36,800
2,600
-2,700
-1,100
-4,300
-2,000
18,100
45,800
0.0
-0.8
1.5
-0.9
7.0
0.3
-0.7
-0.3
-2.3
-0.2
2.7
0.9
Figures may not add due to rounding
In comparing the seventeen-group and ten-group models it should be noted that six GLA ethnic groups are
common to both models. These are the Black Caribbean, Black African, Indian, Pakistani, Bangladeshi, and
Chinese groups. They are the same for both models in Appendix 1, and are equivalent in Table 1. The
remaining GLA aggregated ethnic groups in Table 1 and Appendix 1 are permutations of constituent census
groups. Hence it is important to understand that the Black Other, Other Asian, and Other GLA ten-group
aggregated ethnic groups in Table 1 and Appendix 1 are not of the same definition and composition as the
GLA seventeen-group individual ethnic groups of similar name , i.e. Other Black, Other Asian, and Other
Ethnic Group.
Table 1 indicates that, at Greater London level, for most aggregated ethnic groups the 10from17 overall
ethnic populations for the final projection year did not differ significantly from those produced by the
preceding ten-group model (10AEG). Six groups were less than 1 per cent different, and another three
differed by up to 3 per cent. Only the Black Other group differed more widely, by 7 per cent. Trends of
percentage differences between the 10from17 and 10AEG overall populations for each aggregated ethnic
group over the projection period 2011 to 2014 are shown in Figures 1 and 2. These trends show that small
percentage differences between the two model outputs, in particular within the +/- 1 per cent range, were
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maintained throughout the projection period for most of the ten aggregated ethnic groups at Greater
London level.
Although the greatest 2041 population difference produced by the seventeen-group model was a reduction
of 46 thousand in the White group this was small in relative terms, 0.8 per cent. The corresponding
population gain in the BAME group as a whole was not evenly dispersed among its individual ethnic groups,
with most of the gain arising in the Black Other and Other groups, and the remaining groups showing gains
or losses of a few thousand people each.
% DIFFERENCE 10from17 - 10AEG
Figure 1: % difference between 10from17 and 10AEG over projection period 2011 to 2041:
10 Aggregated Ethnic Groups, R2014 TREND LTM - Greater London
8
1%
6
-1%
White
4
Black Caribbean
2
Black African
0
Black Other
-2
Indian
-4
Pakistani
Bangladeshi
-6
Chinese
2041
2039
2037
2035
2033
2031
2029
2027
2025
2023
2021
2019
2017
2015
2013
2011
-8
Other Asian
Other
PROJECTION YEAR
% DIFFERENCE 10from17 - 10AEG
Figure 2: Figure 1 with expanded scale:
2.0
1%
1.5
-1%
White
1.0
Black Caribbean
0.5
Black African
0.0
Black Other
-0.5
Indian
-1.0
Pakistani
Bangladeshi
-1.5
Chinese
PROJECTION YEAR
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2041
2039
2037
2035
2033
2031
2029
2027
2025
2023
2021
2019
2017
2015
2013
2011
-2.0
Other Asian
Other
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Figure 3 shows the aggregated ethnic group percentage differences between the 10from17 and 10AEG
populations for 2041 for Greater London (in Table 4) broken down by borough. The boroughs are ranked by
percentage difference, independently within each ethnic group, and therefore boroughs do not align for all
their ethnic groups. Hence boroughs are shown as ranks instead of borough names along the x-axis.
For ten aggregated ethnic groups in each of the 33 boroughs there are a total of 330 borough-ethnicities in
London. For 284 of these borough-ethnicities (86 per cent of the 330) the percentage differences between
the 10from17 and 10AEG overall populations for 2041 were within +/- 5 per cent. The distributions in
Figure 3 indicate that for seven aggregated ethnic groups the percentage differences were within the +/- 5
per cent range in almost all boroughs. For the other three aggregated ethnic groups (Bangladeshi, Black
Other, and Other) the percentage differences extended to +15 to -10 per cent in some boroughs.
At single-year-of-age the percentage differences between the 10from17 and 10AEG populations were
greater than corresponding borough ethnic overall population percentage differences. There was also
variation in these percentage differences between single-years-of-age.
Figure 3: % difference between 10from17 and 10AEG, R2014 TREND LTM:
10 Aggregated Ethnic Groups for each London Borough, 2041
15
10
% DIFFERENCE 10from17 - 10AEG
5%
-5%
White
5
Black Caribbean
Black African
Black Other
0
Indian
Pakistani
Bangladeshi
-5
Chinese
Other Asian
Other
-10
-15
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31
33
BOROUGH RANK (each aggregated ethnic group ranked independently)
Some differences in ethnic population outputs between the seventeen-group and ten-group models should
be expected. This is because:
 The final process in the ethnic projection model is to constrain ethnic populations to borough nonethnic populations produced by the main borough demographic projection model. Depending on the
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Ethnic Group Population Projections - Extension To 17 Ethnic Groups
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pre-constrained ethnic populations arising in the ethnic model this will also affect the final differences
between ethnic model outputs that result at single-years-of age.
 For the six ethnic groups (Black Caribbean, Black African, Indian, Pakistani, Bangladeshi, and Chinese)
which are common to both models the ethnic-specific in-migration rates and out-migration probabilities
are the same but are applied to slightly different ethnic populations that arise as a result of the
constraining process as the projection moves away from the base year. For the remaining ethnic groups,
when disaggregated between the two models the resulting ethnic-specific in-migration rates and outmigration probabilities will be different, and they will then similarly be applied to slightly different ethnic
populations arising in each model. So although the underlying census migration data is the same in both
models, ethnic aggregation/disaggregation effects arise between the models.
 There would be an aggregation/disaggregation effect between models in the application of ethnic
fertility rates due to application of disaggregated ethnic fertility rates and also due to application of
fertility rates to slightly different and disaggregated female populations.
 For transgenerational ethnicity of births the ethnicity of infant probabilities and odds ratios in the tengroup model were based on 2001 Census data, whereas for the seventeen-group model they were based
on 2011 Census data. The populations of mothers and fathers that they are applied to then also vary
between the two models as for the ethnic migration parameters and ethnic fertility rates.
 The seventeen-group model uses a single UK-based birth sex ratio with no ethnic or regional variation,
whereas the ten-group model assumed ethnic variation based on census Greater London ethnic 0-year
olds.
In view of these aspects it is considered that the comparison of projected ethnic population differences
between the seventeen-group and ten-group outputs at Greater London level and at borough level is
favourable and is of sufficient consistency to validate use of the seventeen-group model for future ethnic
projections.
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Appendix 1: GLA projection 17 ethnic groups and how they relate to the 2011 Census ethnic groups
GLA ethnic model
seventeen-group
ONS 2011 Census
Ethnic Group (18)
White: English/Welsh/Scottish/Northern Irish/British
White: Irish
White: Gypsy or Irish Traveller 4
White: Other White
Black/African/Caribbean/Black British: Caribbean
Black/African/Caribbean/Black British: African
Black/African/Caribbean/Black British: Other Black
Mixed/multiple ethnic group: White and Black Caribbean
Mixed/multiple ethnic group: White and Black African
Asian/Asian British: Indian
Asian/Asian British: Pakistani
Asian/Asian British: Bangladeshi
Asian/Asian British: Chinese
Mixed/multiple ethnic group: White and Asian
Asian/Asian British: Other Asian
Mixed/multiple ethnic group: Other Mixed
Other ethnic group: Arab 4
Other ethnic group: Any other ethnic group
ONS 2001 Census
Ethnic Category (16)
White: British
White: Irish
White: Other White
Black or Black British: Caribbean
Black or Black British: African
Black or Black British: Other Black
Mixed: White & Black Caribbean
Mixed: White & Black African
Asian or Asian British: Indian
Asian or Asian British: Pakistani
Asian or Asian British: Bangladeshi
Chinese or Other: Chinese
Mixed: White & Asian
Asian or Asian British: Other Asian
Mixed: Other Mixed
Chinese or Other: Other
GLA Ethnic Group
White British
White Irish
GLA ethnic model
ten-group
GLA Aggregated Ethnic Group
GLA
(AEG) 2
White or BAME 1
White
White
Other White
Black Caribbean
Black African
Other Black
White & Black Caribbean
White & Black African
Indian
Pakistani
Bangladeshi
Chinese
White & Asian
Other Asian 3
Other Mixed
Arab
Other Ethnic Group
Black Caribbean
Black African
Black Other
Indian
Pakistani
Bangladeshi
Chinese
BAME
Other Asian 3
Other
1
BAME (Black, Asian and Minority Ethnic) denotes a grouping of all ethnic groups except the white groups.
Approximate to the ten Ethnic Groups used in the 1991 Census, using best fit comparison described in DMAG Briefing 2003/9, 2001 Census Key Statistics: Ethnicity, religion
and country of birth.
3
Although the same name for the Other Asian group is used in both GLA models the definitions are different.
4
These two 2011 Census ethnic groups (Gypsy or Irish Traveller and Arab) were not defined separately in the 2001 Census.
Two additional ethnic groups were introduced in the 2011 Census for England & Wales, “White: Gypsy or Irish Traveller”, and “Other ethnic group: Arab”. To date there is no
detailed Census data or ONS studies thereof available that establish linkage between the 2011 groups and higher-level ethnic group aggregations used in relation to data from
previous Censuses. To allow comparison with previous GLA ethnic projections and permit use of the GLA 10-group ethnic model the two new groups were allocated to the White
and Other GLA Aggregated Ethnic Groups respectively.
2
Note the different terminology used by ONS in the last two censuses for the main White group: “White: British” in the 2001 Census and “White:
English/Welsh/Scottish/Northern Irish/British” in the 2011 Census. It has been assumed that this is the same ethnic group reflecting people who consider themselves of White
background relating to the United Kingdom of Great Britain and Northern Ireland (this excludes White people from the Republic of Ireland, who are defined as a separate group,
White Irish, in both Censuses). Technically this 2011 Census group would be summarised as “White UK”, but is referred to as “White British” for consistency and continuity.
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For more information please contact Ed Klodawski, GLA Intelligence
Greater London Authority, City Hall, The Queen’s Walk, More London, London SE1 2AA
Tel: 020 7983 4694 e-mail: [email protected]
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Copyright © Greater London Authority, 2016
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