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Frequently asked questions about population projections

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This document provides answers to frequently asked questions (FAQs) about population projections, covering national, subnational and marital status projections.

Specific questions about each projection may be answered by the specific FAQ document or methodology document contained within that release. If you cannot find the answer to your question in any of these documents please send any queries to projections@ons.gsi.gov.uk, or telephone 01329 444 652.

About the projections

What are population projections?

Population projections provide an indication of the size and age/sex structure of the future population if specified assumptions about future fertility, mortality and migration were to be realised. They are not forecasts and do not attempt to predict the impact that future government policies, changing economic circumstances or other factors (whether in the UK or overseas) might have on demographic behaviour.

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What population projections are available?

The Office for National Statistics (ONS) produces national population projections, subnational population projections and marital status projections.

National population projections (NPP) for the UK and its constituent countries are prepared by ONS on behalf of the National Statistician and the Registrars General for Scotland and Northern Ireland.

Subnational population projections (SNPP) for local authority areas in England are also published by ONS. Subnational population projections for Scotland are produced by National Records for Scotland, Wales by the Statistical Directorate of the Welsh Government, and Northern Ireland by the Northern Ireland Statistics and Research Agency.

ONS also produces population projections by marital status for England and Wales.

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For what level of geography are projections available?

National projections cover the population of the UK and its four constituent countries.

Subnational projections for England are available for regions (formerly Government Office Regions), Strategic Health Authorities (SHAs), Primary Care Organisations (PCOs), counties and local authorities within England only. Subnational projections for the other countries of the UK are also available; please refer to the question “what population projections are available” above.

Marital status projections are available at England and Wales level only.

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What set of geographic boundaries are used?

The projections use the latest available geographic boundaries provided by ONS Geography. Details on geographic boundaries are made available as part of individual releases.

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How often are population projections published?

National projections are currently produced every two years. Subnational projections are usually published every two years approximately 6 months after the national projections. Projections by marital status are not produced on a regular timetable. The release calendar provides information on when future sets of projections are due for publication.

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Where can I find the latest projections?

The latest projections are all published on the ONS website. 

national population projections

subnational population projections (for England)

population projections by marital status

For the latest subnational data for the other countries of the UK, please refer to the question “what population projections are available” above.

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How far ahead do the projections go?

Projections are uncertain and become increasingly uncertain the further they are carried forward in time. For this reason, analysis of projection results mainly focuses upon the first 10 or 25 years of the projection period, which corresponds with the planning horizons of the majority of users of the projections.

Subnational projections and marital status projections are generally available for up to 25 years ahead.

Some key users require national projections over a longer time period for modelling purposes, and, in accordance with the government’s transparency agenda, national projections are now published for up to 100 years ahead. Caution must be used when interpreting these longer-term projections. National variant projections are also available to aid interpretation of the uncertainty.

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What is a variant projection?

Projections are uncertain and becoming increasingly so the further they are carried forward in time. It is vital that users of population projections, especially those with long-term planning horizons, take account of this uncertainty in their planning.  Therefore in addition to the principal (or central) national projection, variant projections are also published based on alternative assumptions. These variant projections provide an indication of uncertainty by allowing users to consider the impact upon the population if future fertility, mortality and migration differ from the assumptions made for the principal projection. The publication of variant projections is an internationally recognised method for illustrating the uncertainty associated with population projections.

Variant projections are also produced for the marital status projections. ONS do not currently produce variant subnational population projections but this may be considered in the future.

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Are other population breakdowns available? Do you produce population projections by ethnic group, or by religious belief, or by country of birth, or for small areas?

No. There are no official projections of the population by ethnic group, religious belief, country of birth, nor any other population characteristics other than marital status, and there are no official projections for geographies smaller than local authority level. The University of Leeds has undertaken a study, funded by the ESRC, looking at population projections by ethnic group.

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Does anybody else produce population projections?

Eurostat publishes projections for all the EU countries based on the population on 1 January, whereas the ONS projections are based on the population on 30 June. The United Nations (UN) also produces projections for the UK. The UN projections group countries together, therefore in these projections it is assumed that the UK will experience similar trends as the countries it is grouped with. Projections may be generated by other parties, for example some local authorities and academics, though these often differ from ONS projections in data sourced and/or methodology.

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More frequently asked questions on Uses of projections, Definitions, Methodology and Migration

Uses of projections 

Definitions

Methodology

Migration

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