• estimates are available annually by age and sex, from mid-2001 onwards

  • population estimates for middle layer super output areas (MSOA) and lower layer super output areas (LSOA) are designated National Statistics, whereas the remaining estimates are published as experimental Official Statistics

  • mainly based patient registers and child benefit administrative datasets

  • estimates are revised in line with the results of a census

The small area population estimates (SAPE) provide annual estimates of the population at mid-year (30 June), by age and sex. They include population estimates for lower layer super output areas (LSOA), middle layer super output areas (SMOA), health geographies, wards, parliamentary constituencies and national parks in England and Wales.

From mid-2012 onwards, the SAPE can be broken down into 2 main types: the super output area (SOA) estimates (both middle and lower layers), produced using a “ratio change” methodology, and the estimates for other geographies, produced using an “output area apportionment” methodology.

The rationale behind both of these approaches is to use information held in administrative datasets to update estimates of the population year on year, until results from the next census can be used to rebase the data. Full details of the population estimates methodology are available.

The main users of SAPE data are central government, local authorities, the health sector and academics. Initiatives, such as Neighbour Statistics, have meant that population estimates at small area level have become essential.

We quality assure the administrative data used for these statistics to ensure that they are suitable for this purpose. To gain further insight on data quality issues and the impact on statistics, please see Quality Assurance of Administrative Data:

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