National Records of Scotland

Preserving the past, Recording the present, Informing the future

Notes and Definitions

Notes and Definitions

Population Covered

The estimated 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 UK and non-UK armed forces stationed in Scotland are included; UK forces stationed outside Scotland are excluded. Short-term international migrants are excluded.

Age

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

Presentation of Results

Although the populations are tabulated in units, this does not imply accuracy to that level. The data are presented in units for the convenience of users wishing to compile non-standard aggregations without encountering rounding problems.

Administrative Areas

The composition of the NHS Board areas in terms of Council areas is summarised in the table below. This publication does not take into account changes due to the abolition of Argyll & Clyde NHS Board area.

Composition of NHS Board areas

NHS Board area

Council area

Argyll & Clyde

Argyll & Bute, East Renfrewshire (part), Inverclyde, Renfrewshire, West Dunbartonshire (part), Stirling (part)

Ayrshire & Arran

East Ayrshire, North Ayrshire, South Ayrshire

Borders

Scottish Borders

Dumfries & Galloway

Dumfries & Galloway

Fife

Fife (part)

Forth Valley

Clackmannanshire, Falkirk (part), Stirling (part), Perth & Kinross (part)

Grampian

Aberdeen City, Aberdeenshire, Moray

Greater Glasgow

East Dunbartonshire, East Renfrewshire (part), Glasgow City, North Lanarkshire (part), South Lanarkshire (part), West Dunbartonshire (part)

Highland

Highland

Lanarkshire

North Lanarkshire (part), South Lanarkshire (part), West Lothian (part), Falkirk (part)

Lothian

East Lothian, City of Edinburgh, Midlothian, West Lothian (part), Falkirk (part)

Orkney

Orkney Islands

Shetland

Shetland Islands

Tayside

Angus, Dundee City, Perth & Kinross (part), Fife (part)

Western Isles

Eilean Siar

* Note: In practice there are some other very small 'slivers' where NHS Board and Council area boundaries cross.

Land Area

The land areas used to calculate the population density information presented in Table 9 were derived from digital boundaries used for the 2001 Census.

Migration Data Sources

Migration is the most difficult component of population change to estimate. The other components (births and deaths) are estimated using data from the civil registration system, which is considered to be virtually complete. In contrast, there is no comprehensive system which registers migration in the UK - either moves to or from the rest of the world, or moves within the UK. Estimates of migration therefore have to be based on survey data and the best proxy data that exist.  

Migration is derived from three key sources of data. The National Health Service Central Register (NHSCR) for moves between health board areas within the UK, with migration at council area level within Scotland estimated using anonymised data from the Community Health Index (CHI). The International Passenger Survey (IPS) provides information on moves into and out of Scotland from outside the UK. 

The NHSCR system records the movements of patients between NHS health board areas in the UK. Each time a patient transfers to a new NHS doctor in a different health board area, the NHSCR is notified and then the patient is considered to have made a migrant move. Counts of these re-registrations are used as a proxy indicator for moves within the UK.

The CHI holds records of people registered with an NHS doctor in Scotland. Unlike the NHSCR, the records provided to National Records of Scotland (NRS) contain the postcode of the patient's address, which enables migration to be estimated for councils, and for smaller areas. The approach used for estimating council-level migration involves matching CHI patient records which are extracted from a database which reflects the ‘live’ CHI system on two occasions one year apart.

This matching of two extracts, say A and B, will create three sets of patients:

  • set of patients in extract A and extract B
  • set of patients in extract A but not in extract B
  • set of patients in extract B but not in extract A.

The set of patients in both extracts whose postcodes were not the same in each extract can be considered as those within-Scotland migrants who moved from one address in Scotland to another within Scotland between the dates of the two extracts. The remaining two sets of patients are either migrants to or from Scotland; babies born between the two extracts; deaths between the dates of the two extracts; movements to or from the Armed Forces; and a small number of records that are for the same patient but have different CHI numbers because they could not be matched when the GP registration was processed.

Currently, NRS migration data derived from the NHSCR is considered to be the most reliable data available at health board level, so estimates from the CHI are controlled to ensure that they are consistent with the NHSCR data for moves across a health board boundary by origin, destination, age and sex.

The International Passenger Survey (IPS) is a continuous sample survey conducted by the Office for National Statistics at the principal air, sea and Channel Tunnel routes between the UK and countries outside the British Isles. The sample of migrants contacted within the survey is small, particularly for Scottish migrants (approx 100 survey contacts during 2004), and therefore estimates derived from the IPS are subject to larger sampling and non-sampling errors, and are considered less reliable than UK-level estimates. Information about the country of origin and destination, and age of migrants is particularly subject to error. In addition to IPS data, additional information is received on migrants to and from the Republic of Ireland, asylum seekers and visitor switchers [Footnote 1].

International Migration

The method for estimating international migration into and out of Scotland combines data on intentions to migrate to Scotland based on the IPS, along with estimates of data on migration from Ireland, visitor switchers [Footnote 1] and asylum seekers. An estimate for unmeasured migration is also included and this is explained in more detail below.

The Office for National Statistics (ONS) produce an estimate of Total International Migration (TIM) which is similar to this approach, although it includes an adjustment for migrant switchers (people who intend to stay for one year but stay for a shorter period), and use a modified methodology for visitor switchers. More information on ONS’s method can be found in their publication 'Total international Migration 2004' which is available on their website.

In light of ongoing research into the geographical distribution of international migrants, and the methods for estimating visitor and migrant switchers (through the National Statistics Quality Review of International Migration) the method used in Scotland has not been changed. However, it is planned to carry out a full review once the relevant research is completed. 

More details on the Quality Review and the most recent progress report published in September 2006 can be found on the ONS website.

In addition to the results of the quality review, it is planned to analyse recent trends in data relevant to international migration including NHSCR registrations from overseas, accession monitoring reports, applications for National Insurance Numbers and information from the School Census.

Distribution of International Migrants to Scotland

After reviewing the method used to allocate international migration to NHS Board areas and the assumed age/sex distributions, it was decided to make some small improvements to the way in which international out-migrants are allocated to NHS Boards in Scotland, and also to improve the age and sex distributions used for all international migrants. These changes do not affect the method for determining the Scotland total level of international migration.

Previously the estimated Scotland level overseas migration outflow was allocated to NHS Board areas using the proportions recorded in the NHSCR for overseas outflows, even though it is known that the NHSCR under records out-migration to overseas and it is likely that only a sub-group of migrants, possibly families with children remove themselves from their GP’s register. Therefore, in mid-2005 international migration to NHS Boards was allocated by using both overseas outflows and also moves from Scotland to the rest of the UK recorded on the NHSCR. These averaged proportions were used to allocate international outflows from NHS Boards. As in previous years, the proportion of international inflows to NHS Boards in Scotland recorded on the NHSCR were used to allocate the international inflows. A full description of the previous method 'Estimating council area migration' is available on this website.

As well as changing the allocation of overseas outflows from NHS Boards in Scotland the age and sex distribution for overseas migrants, both inflows and outflows was improved. Previously it was assumed that the age and sex of overseas migrants was the same as that of internal and cross border migrants. However, evidence from the 2001 Census has shown that the age and sex distribution of in-migrants from overseas is different to the distribution of internal migrants within Scotland and to/from the rest of the UK. Therefore, it was decided to use the overseas inflow from the NHSCR to give an age and sex distribution to international in-migrants, as when the distribution was compared with census data it was very similar. Unfortunately there is no reliable age and sex information for people leaving Scotland to go overseas. However, it is known from comparing distributions of in and out flows at the UK level from the IPS that the distributions of in and out flows are different. Therefore, it was decided that the international inflow distribution recorded on the NHSCR could not be used for the outflows and investigation showed that the distribution from moves to the rest of the UK recorded by the NHSCR, seemed to give the most plausible alternative, hence it was used.

The issue of how international migration is allocated to NHS Boards will be considered further once the results of the work being carried out as part of the quality review into international migration are known.

Unmeasured Migration

The results of the 2001 Census indicated that the previously published 2000 mid-year estimates had been overestimated by some 50,000 as a result of cumulative errors in estimating migration (mostly by young men) during the 1980s and 1990s. As a result, the migration estimates for 1982-2000 were revised. It is likely that these migration errors are the result of an underestimation of young male migration from Scotland to the rest of the world during this period, but if moves from Scotland to the rest of the UK have been under-recorded, the implied increase in overseas migration would be less.

To ensure that migration estimates do not continue to be overestimated, an adjustment was included in the 2002 and 2003 mid-year estimates. The estimated civilian migration component included an adjustment for unmeasured migration. At the Scotland level, this amounted to an outflow of -2,600. Further investigation has shown that this adjustment should be -1,500 and this is the adjustment which has been used in mid-2004 and mid-2005 estimates. It is planned to look at this element of unmeasured migration again in conjunction with other development work on migration. Further work will make it possible to provide historic estimates of flows between Scotland and the rest of the UK and overseas consistent with the revised population estimates. More information on the cumulative migration error since 1981 can be found in the paper 'Comparisons with Previous Estimates and Implications for Revisions' on this website or by contacting NRSStatistics Customer Services using our Contact Form.

Footnote

1. Visitor switchers are visitors who enter or leave the UK intending to stay in the destination country for less than a year, but who actually stay for a year or longer and therefore become migrants.

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