2021 Census: Safeguarded Individual Microdata Sample at Grouped Local Authority Level (England and Wales)

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The 2021 UK Census was the 23rd official census of the United Kingdom. The UK Census is generally conducted once every 10 years, and the 2021 censuses of England, Wales, and Northern Ireland took place on 21 March 2021. In Scotland, the decision was made to move the census to March 2022 because of the impact of the coronavirus pandemic. The censuses were administered by the Office for National Statistics (ONS), the Northern Ireland Statistics and Research Agency (NISRA) and National Records of Scotland (NRS), respectively. In England and Wales, Census 2021 was the first census with a digital-first design, encouraging participants to respond online rather than on a paper questionnaire.

Topics covered in the 2021 UK Census included:

• demography and migration
• ethnic group, national identity, language and religion
• labour market and travel to work
• housing
• education
• health, disability, and unpaid care
• Welsh and other languages
• UK armed forces veterans
• sexual orientation and gender identity.

The 2021 Census: Safeguarded Individual Microdata Sample at Grouped Local Authority Level dataset consists of a random sample of 5% of person records from the 2021 Census. It includes records for 3,021,611 persons. These data cover England and Wales only. The lowest level of geography is grouped local authority. This means groups of local authorities or single local authorities where the population reaches at least 120,000 persons. The dataset contains 87 variables and a low level of detail.

Census Microdata

Microdata are small samples of individual records from a single census from which identifying information have been removed. They contain a range of individual and household characteristics and can be used to carry out analysis not possible from standard census outputs, such as:

• creating tables using bespoke variable combinations
• investigating specific combinations of variables or categories in a high level of detail
• conducting non-tabular statistical analyses on record-level data.

The microdata samples are designed to protect the confidentiality of individuals and households. This is done by applying access controls and removing information that might directly identify a person, such as names, addresses and date of birth. Record swapping is applied to the census data used to create the microdata samples. This is a statistical disclosure control (SDC) method, which makes very small changes to the data to prevent the identification of individuals. The microdata samples use further SDC methods, such as collapsing variables and restricting detail. The samples also include records that have been edited to prevent inconsistent data and contain imputed persons, households, and data values. To protect confidentiality, imputation flags are not included in any 2021 Census microdata sample.