GLA 2024-based housing-led population projections

Citation: © GLA 2024-based demographic projections

For questions about the projections or advice on their use, email the team at:  demography@london.gov.uk

Publisher information:
City Data Team
City Intelligence
Greater London Authority
City Hall, Kamal Chunchie Way, London, E16 1ZE
https://www.london.gov.uk/

# Notes:
1. All estimates and projections relate to mid-year of the indicated year.
2. Data relate to local authority district boundaries as they existed in December 2023
3. Data are provided with limited rounding to facilitate their onward use. The apparent precision of data should not be mistaken as a declaration of accuracy.  All outputs should be considered as containing significant levels of uncertainty. Totals may not match due to rounding.
4. Population data are for the ‘usually resident population’ based on the United Nations definition and includes international arrivals expect to be present for at least a year. 
5. Projections are produced for all local authority districts and regions in England. Two sets of outputs are currently published: one including data for London local authorities, London (region-level), and England (country-level); the other including data for all local authorities and regions.

# Included outputs

* households.csv - households by type, and age group and sex of representative person
* population.csv - population by age group, sex, and residence type
* household_representative_rates.csv - household representative rates by household type, and age group and sex of representative person
* household_totals_by_type.csv - total households by type
* population_household_totals - population totals by residence type, total households, average household size

# Overview of household projections

* A population projection based on past trends of fertility, mortality and migration is produced

* The projected population is split into those resident in private households and those in communal establishments (CE)

* Household Representative Rates (HRR) - the ratio of persons considered the representative of a household to the number of persons in the private household population - are calculated from past census data

* Past household representative rates are extrapolated forward for future years and then applied to the projected household population to give projected households

Each of these steps are performed by local authority, age group, sex, and household type. 

The number and type of households projected by the model are dependent on:

* the size, age/sex structure, and spatial distribution of the projected population

* the assumptions used to split the population between private households and communal establishments

* the method used to project forward household formation rates

# Included projection variants

Multiple variants of household projection are included in these outputs, based on combinations of scenarios of future population, household representative rate, and communal establishment population.

Population scenarios: 
* central, high, low variants of the GLA 2024-based trend projections

Household representative rate scenarios:
* 10yr_return_2001 - return to past levels of household formation over 10 years. Rates for each age group, sex, and household type return to at least the same levels as they were in 2001 over a 10-year period (2026 to 2036).
* 20yr_return_2001 - return to past levels of household formation over 20 years. Rates for each age group, sex, and household type return to at least the same levels as they were in 2001 over a 20-year period (2026 to 2046).
* constant_2021 - rates held at levels captured in the 2021 census for the duration of the projection period.
* exp_2001_21 - continuation of past trends. Generated using the same two-point exponential method employed by ONS in the 2018-based subnational household projections, but updated to incorporate the results of the 2021 census.  Trends are based on the period 2001 to 2021 and rates are projected forward 20 years to 2041, before being held constant.

Communal establishment population:
* constant_number - number of persons resident in communal establishments assumed to remain fixed at 2021 levels for all age groups
* constant_rate_75over - number of persons resident in communal establishments assumed to remain fixed at 2021 levels up to age 74. For older age groups, the *proportion* of the population resident in communal establishments is assumed to remain constant.


