How to use forecasts, estimates and projections

Hampshire County Council publishes a number of population estimates, each providing slightly different numbers of people in Hampshire. It can be unclear which figure to use, when to use it and why the figures differ.

No matter which set of figures are used, they will only be an estimate of the population and should be treated as such.

Some figures on these pages are provided down to the individual person, which gives users the flexibility to add values up to their chosen age and area groupings. However, to emphasise the fact that these are estimated figures, we recommend rounding the figures to the nearest 10 or 50 people when publishing elsewhere.

Population estimates

Every 10 years a census of the population is carried out. This is the only time a full count of the population is taken.

Between censuses there is a need to understand the size of a population and its characteristics. Population estimates are produced with the aim to get close to the real, unknown number as possible.

There are different 'between census' population estimates and each estimate type uses different assumptions, and it is important to know how each figure is produced. These assumptions can result in varying numbers.

Small Area Population Forecasts (SAPF)

Produced by Hampshire County Council, SAPF data provides estimates of the current population and future population over the next seven years. The 2011 Census is the base for this set of figures. SAPF makes use of local information on children, dwelling completions and the locations of planned dwellings. SAPF is available at small geographical areas, including districts, wards and parishes.

When to use SAPF

  • The most accurate picture of Hampshire's population now and over the next seven years
  • Key source for information on areas smaller than district level
Long term population projections (what the population may look like in 20+ years’ time)

There are two sources of projections.

Office for National Statistics Sub National Population Projections (SNPPs)

Subnational population projections provide statistics on potential future population levels, based on the continuation of recent demographic trends and assumptions used in the national population projections. These projections are not forecasts and do not attempt to predict the impact of future political and economic changes or local development policies. They are produced for all Local Authorities, so the data can be compared in a consistent way across the whole country.

The projected local authority populations for each year are calculated by ageing on the population from the previous year, applying local fertility and mortality rates to calculate the projected births and deaths, and then adjusting the migration into and out of each local authority. The local fertility, mortality and migration assumptions are estimated based on the trends from the last five years. These trends are then projected forwards. These projections therefore provide an indication of the longer term demographic impact of existing trends and existing policies if they were to continue.

Hampshire County Council Long Term Population Projections

As recognised by ONS, the projections do not take into account any increased level of house building which is likely to happen over the time period of the projections. As advised by ONS therefore, the County Council seeks to supplement these projections with local intelligence relating to ‘policy on’ housing growth strategies that are being developed. The resultant long term population projections, use the ONS Sub National Population Projections as its basis, before modelling the potential impact of planned growth rates across the county. The outputs are provided at district level.

When to use population projections

  • Looking at long term population of Hampshire
  • ONS figures allow comparisons with other areas, but unlike Hampshire County Council long term projections do not take additional dwellings into account
Office for National Statistics Mid-Year Estimates (MYE)

Produced by the Office for National Statistics (ONS), MYE figures provide estimates of the current population at Local Authority level across the whole country.

When to use Mid-Year Estimates (MYE)

  • An alternative to Hampshire's SAPF figures at the local authority level
  • Key source for comparing Hampshire's population with other parts of the country

For guidance on which population figures are the most appropriate to use, please contact [email protected]