National population projections are prepared by the Office for National Statistics on behalf of the National Statistician and the Registrars General of Scotland and Northern Ireland. The assumptions are agreed in liaison with the devolved administrations, following consultation with key users of projections in each country and advice from an expert academic advisory panel.

National population projections by age and sex are produced for the UK and its constituent countries every two years. The projections are based on the most recently available mid-year population estimates and a set of underlying demographic assumptions regarding fertility, mortality and migration. They are not forecasts and do not attempt to predict the impact that future government policies, changing economic circumstances or other factors might have on demographic behaviour.