Overview
Microdata are small samples of individual records from a single census and from which we have removed any identifying information. They contain a range of individual and household characteristics which means that you can use them to carry out analysis not possible from standard census products. Microdata samples range in size from 10% to 1% of households or individuals.
Protecting confidentiality
We protect the confidentiality of individuals and households in our microdata samples by:
restricting access to them
removing information that might identify a person, such as names, addresses and date of birth
applying statistical disclosure control (SDC) methods to the microdata samples, or making changes to data to protect identity, for example, record swapping, collapsing variables and restricting detail
Read more about SDC in Protecting personal data in Census 2021.
Census 2021 microdata samples for England and Wales
There are four types of Census 2021 microdata samples for England and Wales. They are:
public microdata teaching sample
safeguarded microdata samples
Integrated Public Use Microdata Series (IPUMS) microdata sample
secure microdata samples
Public microdata teaching sample
Access
Our public microdata teaching sample is available to download from our website with minimal conditions applied to their use as stated within the Open Government Licence (OGL).
About
Our public microdata teaching sample consists of a random sample of 1% of person records from Census 2021 for England and Wales. It includes records for 604,351 persons. The sample is useful for people teaching or learning about statistics and social sciences.
The lowest level of geography is Wales and regions within England. It contains 19 variables and a low level of detail.
Release date
Our public microdata sample was released on 7 September 2023.
Safeguarded microdata samples
Access
Our safeguarded microdata samples are only available to data analysts through the UK Data Service in line with previous censuses. Data analysts must register with the UK Data Service and agree to the terms and conditions of the UK Data Service End User Licence.
About
Safeguarded individual microdata sample at region level
This consists of a random sample of 5% of person records from Census 2021; it includes records for 3,021,455 persons. The lowest level of geography is Wales and regions within England. It contains 89 variables and a medium level of detail.
Safeguarded individual microdata sample at grouped local authority level
This consists of a random sample of 5% of person records from Census 2021; it includes records for 3,021,611 persons. 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. It contains 87 variables and a low level of detail.
Safeguarded household microdata sample
Consists of a random sample of 1% of households from Census 2021 and contains records for all individuals within these sampled households; it includes records for 263,729 households and 606,210 persons. This sample allows linkage between individuals in the same household. The lowest level of geography is Wales and regions within England. It contains 56 variables and a low level of detail. This is a new product following user feedback from 2011 Census.
Release date
Our safeguarded microdata samples was released on 18 October 2023.
Integrated Public Use Microdata Series microdata sample
Access
Our Integrated Public Use Microdata Series (IPUMS) microdata sample is available to analysts on the IPUMS International website. Analysts need to register, provide information on their project and agree to the terms and conditions of access.
The unharmonised source IPUMS sample is available on the UK Data Service website to analysts who have registered and agree to the terms and conditions of the UK Data Service End User Licence. Commercial use of the data is subject to licensing and each project incurs administrative fees.
About
Our Census 2021 IPUMS household microdata sample consists of a random sample of 1% of households and contains records for all individuals within these sampled households. The IPUMS sample size is the same as for our safeguarded household microdata sample and both these samples exclude households containing more than eight people.
Our IPUMS microdata sample contains records for 263,730 households, 605,103 persons; for households containing no enumerated persons, records in the sample will only include household-level data. The lowest level of geography is Wales and regions within England. It contains 33 variables and a low level of detail.
The IPUMS International project harmonises data provided by countries to enable international comparison. The data supplied to IPUMS is available in both harmonised and unharmonised formats.
Release Date
The IPUMS unharmonised microdata sample will be available to access in early 2024.
Secure microdata samples
Access
Our secure microdata samples are only available to accredited researchers through the Integrated Data Service. Read how to become an accredited researcher.
About
Secure individual microdata sample
This consists of a random sample of 10% of person records from Census 2021; it includes records for 6,204,787 persons and empty household spaces. The lowest level of geography is local authority. It contains 189 variables and a high level of detail.
Secure household microdata sample
This consists of a random sample of 10% of households from Census 2021 and contains records for all individuals within these sampled households; it includes 2,641,775 households and 6,097,307 persons and empty household spaces. This sample allows linkage between individuals in the same family or household. The lowest level of geography is local authority. It contains 194 variables and a high level of detail.
Release date
The secure microdata samples will be available to access in early 2024.
Using the microdata samples
To help you use, analyse, and interpret Census 2021 microdata samples read our User guide to Census 2021 microdata samples, England and Wales. The guide also gives more information about the differences between accessing and using secure, safeguarded and public microdata samples.
The comparability of our microdata samples with Census 2021 is available in our Comparing microdata samples with Census 2021 dataset. This dataset provides univariate and multivariate comparisons to demonstrate how representative the samples are compared with Census 2021 as a whole.
You can find all the variables contained in our microdata samples and the output categories for these variables in our Microdata sample codes: Census 2021 dataset. You can filter the file to show the information for each sample separately.
Census microdata for major data linkage projects
As census microdata samples do not contain information that can identify individuals, researchers will not be able to use these for data linkage purposes.
Where accredited researchers can prove the samples do not provide sufficient utility for major data linkage projects or projects which show major public policy impact, 100% Census 2021 microdata exist within the Integrated Data Service (IDS). This dataset includes personal identifiers and is available for data linkage across other administrative and survey data. Access and usage of these data are very strictly controlled since they contain identifiable information.
Researchers can make a request for datasets to be linked by the ONS if they can show that there is a wider research benefit beyond their individual project. If a request is agreed, the dataset is linked internally and then the de-identified version would be transferred to the IDS so that all accredited researchers are able to make a project application to use it. Researchers wanting to make a request for a linked dataset should email adrcuration@ons.gov.uk.
UK census microdata
Our Census 2021 microdata samples cover England and Wales. To read about similar products for Northern Ireland and Scotland, visit the Northern Ireland Statistics and Research Agency and National Records of Scotland.
In England, Wales, and Northern Ireland the census was conducted in March 2021. In Scotland, the decision was made to move the census to March 2022 because of the impact of the coronavirus pandemic. Take this difference into account when performing any UK-wide analyses using census microdata.
Working with others
A range of internal and external stakeholders helped us to design, create and disseminate Census 2021 microdata samples so that we could best meet our users’ needs.
Internal members of our working group included topic experts on:
migration
travel to work
demography and census transformation
population estimates
statistical disclosure control
External members of our working group included:
National Records of Scotland
Northern Ireland Statistics and Research Agency
Welsh Government
UK Data Service
local authorities
academia
market researchers
commercial researchers
community group
More information
If you have any questions about Census 2021 microdata samples, please email census.customerservices@ons.gov.uk.