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Autumn 2002
NO 109
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Population Trends
In this issue
Page
In Brief
2
Demographic indicators
8
Rebasing the annual mid-year population estimates for England and Wales A description of the methodology to be used for rebasing mid-year population estimates figures following the publication of the results of the 2001 Census Craig Duncan, Roma Chappell, Jonathan Smith, Liz Clark and Francesca Ambrose
9
Variant population projections for the United Kingdom and its constituent countries Details of the full range of variant projections available from the 2000-based national population projections with key results for the UK and individual countries Chris Shaw
15
Local marriage markets in Great Britain: how diverse? An investigation into the extent of differences in the availability of potential marriage partners between different local areas Máire Ní Bhrolcháin, Tom Wilson and Wendy Sigle-Rushton
27
The effect of changes in timing of childbearing on measuring fertility in England and Wales An examination of proposed methods to adjust period fertility data to take account of changes in the timing of childbearing Steve Smallwood
36
One-parent families – and the dependent children living in them – in Great Britain Final estimates of the number of one parent families and dependent children living in them from 1995 to 1997, plus provisional estimates from 1998 to 2000 John Haskey
46
Tables List of tables Tables 1.1 – 9.3 Notes to tables Report: Internal migration estimates for local and health authorities in England and Wales, 2001 Annual Update: Marriages and divorces during 2000 and adoptions in 2001, England and Wales
London: TSO
58 59 86
87
100
Population Trends 109
Autumn 2002
in brief Changes to Health Areas
dropped and subsequent tables in Section 1 renumbered. The table giving population estimates for GORs (Table 1.4 in previous editions, now Table 1.3) now represents Health as well as Administrative Regions. Similarly, reference table 6.2 that used to show deaths for Health Regional Office areas in England has been changed to present deaths for GORs.
The first changes to the structure of the NHS in England as part of Shifting the Balance of Power came into effect on 1 April 2002. Shifting the Balance of Power is the programme of change intended to empower patients and frontline staff in the NHS. It is part of the implementation of the NHS Plan.
Further information on Shifting the Balance of Power can be found on the DH website: www.doh.gov.uk/shiftingthebalance/index.
The main feature of the changes in structure has been to give some 300 locally-based Primary Care Trusts the role of running the NHS and improving health in their areas. This has meant abolishing the previous 95 Health Authorities and creating 28 new ones that serve larger areas and have a more strategic role. The Department of Health (DH) is also refocusing to reflect these changes, including the abolition of its Regional Offices. At 1 April 1999 there were eight DH Regional Offices. Their functions are being transferred as appropriate to the new health structures, including a DH public health function in each of the nine Government Offices for the Regions (GORs). This transfer is planned over the period from 1 April 2002 to 31 March 2003 when the DH Regional Offices will officially be abolished. Government Office Regions North East North West Yorkshire and the Humber East Midlands West Midlands East
The ONS will be changing its outputs for health areas to reflect the new health structures. This process has started in this edition of Population Trends. The reference table presenting population estimates for Health Regional Offices areas in England (Table 1.3 in previous editions) has been
Directorates of Health and Social Care
} }
North
Midlands and Eastern
London South East South West
From 1 April 2002 there are four Directorates of Health and Social Care (DHSCs) within the Department of Health. Their responsibilities include the oversight and development of health and social care, the performance management of the new Strategic Health Authorities, the development and succession of senior staff, supporting Ministers through casework, etc, and troubleshooting as necessary. The GORs sit within the DHSCs as follows:
London
} National Statistics
South
2
Quarterly Population Estimates Population statistics are used by national and local government for planning and monitoring purposes and in resource allocation. Another important use of these population statistics is to provide population controls for grossing results from sample surveys to represent the whole population and, in particular, for grossing the results from the Labour Force Survey (LFS). The LFS is a continuous household survey that is carried out by ONS by interviewing people about their personal circumstances and work. The results from the sample are grossed to represent the whole population and are published about six weeks after the quarter to which they relate. To enable the sample to represent the whole population, grossing needs to take place. At present, the mid year population estimates for the UK are not available until 14 months after the date to which they relate. As LFS results are published 6 weeks after the reference period, more timely grossing totals are required. At present population projections are used, these assumptions are based on past trends in fertility, mortality and migration continuing into the future. The accuracy of
Population Trends 109
projections compared with estimates is dependent on how closely these assumptions reflect what actually happens. These assumptions are particularly difficult to get right in times of unexpected population change, for example during recent years when there have been unprecedentedly high levels of net inward migration. Neither the annual population estimates nor the population projections, meet the LFS needs for grossing totals. Therefore ONS have started work to produce quarterly population estimates (QPEs). These will take advantage of more recently available data on births, deaths and net migration, but will still be subject to revision.
The changes were:
A research project has been set up to research the most appropriate method to produce QPEs. This will involve the evaluation of existing demographic methods such as methods adopted by other National Statistical Offices and other statistical techniques, such as Time series analysis, regression, etc. Research will also take place to determine the levels of geography most suitable to produce QPEs. Predefined evaluation criteria will be used to assess the methods. Resultant QPEs will also be tested against the current mid year estimates to ensure that the best estimate is produced. The first set of estimates should be available by Autumn 2003. These will represent Q3 and Q4 for 2002 and Q1 and Q2 for 2003, then every 6 weeks after the end of the quarter thereafter. Whilst the main customer will be the LFS, the QPEs can also be used to meet the needs of others, who for example require population estimates at the start of the year rather than the middle.
●
If you would like any further information about the ONS project or would like to feed in your views as a potential user; please contact: Lucy Vickers
[email protected] or Rachel Dowell
[email protected]
NS SEC comparability over time: births and infant deaths Introduction An article in Population Trends 107, Spring 20021 described changes in occupational and socio–economic classifications which took place in 2001, and their implications for vital statistics. The effect of these changes was described using data on deaths in the first quarter of 2001. This short report extends that analysis to births and infant deaths, using data from the second quarter of 2001.
●
●
Registrar General’s Social Class (RGSC) was replaced by the new National Statistics Socio-Economic Classification (NS SEC). The full method of deriving NS SEC requires information on occupation, employment status and size of organisation. However the latter is not available on vital events. Therefore NS SEC is assigned to vital events based on occupation and employment status; The Standard Occupational Classification (SOC) was updated from SOC90 (used from 1991 to 2000) to a new revision, SOC2000; The coding of employment status on vital statistics was changed to be consistent with Census coding and the design of SOC2000.
Autumn 2002
Key findings
NS SEC is based on the most recent occupational classification, SOC2000. For data coded to SOC90 (the previous classification) an approximation of NS SEC, referred to as NS SEC90, can be derived. To allow comparisons over time comparability between NS SEC and NS SEC90 improved by recoding old data to the new employment status coding rules. A full explanation is given in Population Trends 107.
●
Analysis of births in the second quarter of 2001 showed that, for 82 per cent of births, the NS SEC90 subcategory was the same as the NS SEC sub-category. 16 per cent of births were assigned to a different NS SEC subcategory as a result of the change from SOC90 to SOC2000 occupational coding. 2 per cent of births were assigned to a different NS SEC sub-category because Registrar’s employment status only approximates to the new employment status coding rules.
●
Analysis of infant deaths in the same period showed that, for 78 per cent of deaths, the NS SEC90 sub-category was the same as the NS SEC subcategory. 18 per cent of infant deaths were assigned to a different NS SEC sub-category as a result of the change from SOC90 to SOC2000. 4 per cent of infant deaths were assigned to a different NS SEC subcategory because Registrar’s employment status only approximates to the new employment status coding rules.
●
Comparability between NS SEC and NS SEC90 was lower for births and infant deaths than for other deaths. 1 This is likely to be because the occupations of younger people are more affected by changes to the occupational classification, and the age distribution of fathers in a given year is younger than the age distribution of men who die in that year.
●
Comparability varies according to NS SEC analytical class, age, sex, and SOC90 or SOC2000 major group. For example, it is lower for managerial and professional groups and for some occupational groups, particularly associate professional and technical occupations and personal service occupations.
Figures presented NS SEC and NS SEC90 are assigned to the ten per cent of live births on which occupation is coded to both SOC90 and SOC2000 in the second quarter 2001. For the purposes of this comparison only births in marriage or outside marriage jointly registered by both parents are included, and the coding is based on father’s occupation only. Table 1 overleaf shows agreement rates between NS SEC90 and NS SEC, that is, the proportion of births which were assigned to the same NS SEC sub-category within each analytic class. There are three columns presenting agreement rates. The first column shows agreement rates given NS SEC90 derived using the previous employment status coding rules. The second shows the agreement rate when NS SEC90 is derived using the Registrar’s employment status code, an approximation to the new employment status coding. The third shows agreement rates between NS SEC and NS SEC90 using the new employment status coding rules. The third column therefore shows what the agreement rates would be if there had only been a change in the occupational coding. Table 2 shows similar information for infant deaths. Less detail is shown in the table because of the small number of infant deaths compared to the number of births.
3
National Statistics
Population Trends 109
Table 1
Autumn 2002
Percentage of second quarter births 2001 allocated to the same NS SEC90 category given their NS SEC category
England and Wales Percentage agreement between NS SEC and NS SEC90 NS SEC90 calculated using SOC90 and old rules employment status code
NS SEC90 calculated using SOC90 and Registrar’s employment status code*
NS SEC90 calculated using new rules employment status code†
All
72.0
81.9
83.6
By NS SEC: 9 class 1.1 Large employers and higher managerial 1.2 Higher professional 2 Lower managerial and professional 3 Intermediate 4 Small employers and own-account 5 Lower supervisory and technical 6 Semi-routine 7 Routine Other
74.4 72.7 57.4 77.0 80.0 46.1 84.9 89.0 93.6
74.1 73.5 73.2 76.9 92.1 86.9 84.0 87.4 93.9
74.5 73.8 74.4 77.4 97.0 88.0 85.2 89.6 94.7
By NS SEC: 5 class 1 Managerial and professional 2 Intermediate 3 Small employers and own-account workers 4 Lower supervisory and technical 5 Semi-routine and routine Other
65.0 77.0 80.0 46.1 87.2 93.6
73.4 76.9 92.1 86.9 85.9 93.9
74.3 77.4 97.0 88.0 87.7 94.7
By NS SEC: 3 class 1 Managerial and professional 2 Intermediate 3 Routine and manual Other
65.0 79.0 73.0 93.6
73.4 87.4 86.3 93.9
74.3 90.9 87.8 94.7
By age
