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Scotland's Population 2001: The Registrar General's Annual Review of Demographic Trends

APPENDIX 2 – NOTES AND DEFINITIONS

This Appendix gives some general notes on some of the data and conventions used in this report as well as providing definitions for some of the terminology used.

GENERAL

Throughout this report the Registrar General’s annual mid-year estimates of population are used for comparing population trends and for use as denominators in calculating rates per head. Rates presented for 2001 use the latest 2001 mid-year estimates based on the 2001 Census. These population estimates are considerably less than the previously published 2000 estimate and will be revised in February 2003 along with earlier series back to 1982. This difference will affect the comparison of rates over time, particularly 2000 and 2001, but is unlikely to significantly alter the trend.

More information on the 2001 mid-year estimates, the reasons for the difference and the revised series is provided within the population section of this Appendix.

— tabular conventions

Where a range of years is listed in a time series table, e.g. 1951-55, the data presented will be an average for this period.

Throughout the tables ‘year’ means ‘calendar year’ except where otherwise defined. By convention, many of the time series presented start at census years e.g. 1991.

— date of registration and place of occurrence

All the data presented on births, stillbirths, marriages and deaths relate to the date of registration of the event and not to the date of occurrence; for example, a birth on 31 December 2000 which was registered on 5 January 2001 would be included in the 2001 figures. Births and stillbirths are usually registered within the statutory period of 21 days. Similarly, marriages are usually registered within 3 days and deaths within 8 days.

Births, stillbirths, and deaths have been allocated to the area of usual residence if it is in Scotland, otherwise to the area of occurrence. Marriage figures relate to the area of occurrence.

POPULATION

All population figures refer to estimates as at 30 June of the year in question.

— population covered

The resident population of an area includes all those usually resident there whatever their nationality. Students are treated as being resident at their term-time address. Members of HM and non-UK armed forces stationed in Scotland are included; HM forces stationed outside Scotland are excluded.

— age

Population figures relate to 30 June of the year shown and ages relate to age last birthday.

— commentary on the 2001 Mid-Year Estimates

The estimated population of Scotland on 30 June 2001 was some 50,400 less than the 2000 mid-year estimates published in April 2001. The fall from the 2000 figure does not represent change in a single year since the previous 2000 estimate was derived by ‘rolling forward’ the 1991 population taking account of births, deaths and migration. Given the new baseline established by the 2001 Census, it will be necessary to revise previous population estimates. In order to provide an indicator of recent change in the population, which may be particularly useful if calculating rates per head, a set of provisionally revised 2000 mid-year estimates has been produced and these are available from GROS Customer Services.

— reasons for the difference

It is expected that the difference of some 50,000 is largely attributable to errors in previous estimates of migration in the 1980s and 1990s. It has been well documented that migration is the most difficult component of population change to estimate because of the lack of a wholly reliable source of data on migration.

The errors in estimating migration in the 1980s will also have affected the adjustments made to the 1991 Census counts to take account of underrenumeration. The adjustments to 1991 Census counts were excessive and added some people, particularly young men, to the population whom we now believe had actually migrated out of Scotland rather than having been missed by the 1991 Census.

A key implication of this difference is the need to revise the mid-1991 figures since there is now evidence that these were too high. Consequently, there will be a need to revise the population figures for each area since 1982. A revised set of population estimates for 1982-2000 will be available by end February 2003.

— population projections

Population projections for Scotland are prepared by the Government Actuary, at the request of and in consultation with, the Registrar General. The latest projection was 2000-based. Earlier this year GROS published sub-national projections for the administrative areas of Scotland that are consistent with the Scotland projection.

The 2000-based population projections for Scotland and its administrative areas used the previously published 2000 mid-year estimates as a base, which are some 56,000 higher than the provisionally revised 2000 mid-year estimates (consistent with the 2001 Census results). While the 2000-based projections are in need of updating, the general picture of a slowly declining population is unlikely to change.

The Government Actuary’s Department plan to publish a set of ‘interim’ 2001-based projections for the UK and its constituent countries. These will not take full account of the results of the 2001 Census but will use the latest population estimates as the new base and will reconsider the migration assumptions in light of the recent results and previous overestimates of migration.

A set of 2002-based projections for Scotland, which take full account of the 2001 Census, is planned for November 2003.

BIRTHS

— total fertility rate (TFR)

The average number of children that would be born to a cohort of women who experienced, throughout their child-bearing years, the fertility rates of the calendar year in question.

— age specific fertility rate (ASFR)

The number of births per individual for a specific age during a specified time.

— cohort

A well-defined group of people who have had a common experience or exposure who are observed through time. For example, the birth cohort of 1900 refers to people born in that year.

— marital status of parents

Married parents: refers to parents who are married to each other. Unmarried parents: refers to parents who are unmarried or married but not to each other.

DEATHS

— cause-of-death coding

From 1 January 2000, deaths in Scotland have been coded in accordance with the International Statistical Classification of Diseases and Related Health Problems (Tenth Revision) (ICD10). Classification of underlying cause of death is based on information collected on the medical certificate of cause of death together with any additional information provided subsequently by the certifying doctor. Changes notified to GROS by Procurators Fiscal are also taken into account. In cases of homicide, intentional self-harm (suicide) and other deaths from violence, advice may be sought from the Crown Office.

— expectation of life

The average number of additional years a person could expect to live if current mortality trends were to continue for the rest of that person’s life. Most commonly cited is life expectancy at birth.

— age standardisation

A straight comparison of crude rates between areas may present a misleading picture because of differences in the sex and age structure of the respective populations. The technique of standardisation has been used in certain tables and charts to remedy this. In general, standardisation involves a comparison of the actual number of events occurring in an area with the aggregate number expected if the age/sex specific rates in the standard population were applied to the age/sex groups of the observed population.

— stillbirth

Section 56(1) of the Registration of Births, Deaths and Marriages (Scotland) Act 1965 defined a stillbirth as a child which had issued forth from its mother after the 28th week of pregnancy and which did not breathe or show any other sign of life. The Still-Birth (Definition) Act 1992, which came into effect on 1 October 1992, amended Section 56(1) of the 1965 Act (and other relevant UK legislation), replacing the reference to the 28th week with a reference to the 24th week.

— perinatal

Refer to stillbirths and deaths in the first week of life.

— infant

Refer to all deaths in the first year of life.

MARRIAGES

Civil marriages were introduced by the Marriage (Scotland) Act 1939, which came into operation on 1 July 1940.

DIVORCES

The data presented on divorces relate to the date on which the decrees were granted.

In legal terms the 1976 Act introduced a single ground for divorce - irretrievable breakdown of marriage - with the detailed reasons as ‘proofs’. However, the information presented in this report on reasons for divorce retains the terminology ‘grounds for divorce’.

ADOPTIONS

The Registrar General for Scotland registers adoptions under the Adoption of Children (Scotland) Act 1930.

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