Population projections by local authority and year
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2018Metadata
- Summary information
- High level information
- Statistical quality information
- Keywords
- Weblinks
- Open Data
General description
This dataset provides population projections for local authorities in Wales by sex, single year of age and each year from the base year of 2018, through the projection period to 2043. This is the fifth set of population projections published for the 22 local authorities in Wales.Note that the projections become increasingly uncertain the further we try to look into the future.
Data collection and calculation
Population projections provide estimates of the size of the future population, and are based on assumptions about births, deaths and migration. The assumptions are based on past trends. Projections only indicate what may happen should the recent trends continue. Projections done in this way do not make allowances for the effects of local or central government policies on future population levels, distribution and change.The 2018 population estimates have been used as the base for the local authority projections. The projected population is for 30 June each year. The base population estimates are based on the usually resident population. Usual residents away from home temporarily are included, but visitors are excluded. Students are counted at their term-time address. It should also be noted that the UN definition of an international migrant is used - those changing country of residence for a period of at least 12 months. Short-term migrants (e.g. migrant workers from Eastern European countries) are not counted in the population estimates and hence are not included in the population projections. The projections are based on an assumed pattern of migration based on projecting forward the average migration patterns over the last five years.
The Chief Statistician published an update in February 2020, giving an overview of the methodological changes that had been made to the local authority projections since the 2014-based local authority projections. This included:
• changing the assumptions for internal migration, so that they were based on migration rates rather than fixed numbers
• constraining the sum of the local authority population projections, and some of the component parts, for the 22 local authorities in Wales to the 2018-based national population projections published by the ONS
Another update was issued in July 2020, announcing the publication date for the revised local authority population and household projections, and the decision to revert to not constraining the local authority population projections.
Following discussions with the Wales Subnational Projections (WaSP) group, we made the decision to revert, in part, to the previous methodology for calculating local authority population projections by removing the constraining to the national population projections. The decision to constrain to the national population projections initially was made as a result of the incorrect national population projections showing a different trend to the local authority population projections. However, as this is no longer the case, we have reverted to the original methodology of not constraining in order to provide better continuity with previous local authority population projections, so that they are mainly driven by local trends for births, deaths and migration.
We have, however, retained the change made to the assumptions for internal migration so that they continue to be based on migration rates rather than fixed numbers. Further information can be found in the update.
We will continue to refine this methodology prior to our next set of subnational projections and take account of user feedback.
Five additional variant projections are also published alongside the principal projection. This includes a low population variant and a high population variant, as well as three variants based on alternative migration assumptions. These are a zero migration variant, a 10-year average migration variant and a 15-year average migration variant.
Frequency of publication
Every two to four yearsData reference periods
Data are published for the period 2018 to 2043.Users, uses and context
See the local authority population projection statistical release in weblinks.Rounding applied
Data are rounded independently to the nearest whole number and may not add exactly.Revisions information
These data replaced the 2014 local authority population projections for Wales as the formal estimates of population growth.On Monday 18 May 2020, the ONS issued a notice on its website informing users that they had identified an error affecting the 2018-based national population projections. The error was caused by incorrect processing of cross-border flows between Wales and England, resulting in the projected mid-2028 population for Wales being approximately 65,000 too low, and that for England being approximately 65,000 too high.
Having consulted with our expert group about the implications for our statistical products that were based on the 2018-based national population projections, we decided to withdraw the 2018-based local authority population projections and household projections.
The ONS published corrected national projections for Wales on Thursday 11 June. These local authority projections are based on the corrected 2018-based national population projections for Wales. Further information about the corrections can be found in the 2018-based local authority population projections release, as well as an analysis of how these corrected projections compare with the previously published projections.
