Integrated census outputs are multivariate, small-area statistical outputs produced by linking administrative data to census responses at record level.
Census 2021 is our first online census. This will allow us to make increased use of administrative data and surveys to both enhance the statistics from Census 2021 and improve statistics between censuses.
Administrative data are data that people have already provided to the government, for example, while accessing public services such as education and healthcare. Some of this information could be re-used by the Office for National Statistics (ONS) to produce statistics about the population.
How we are using admin data in Census 2021 outputs
The Office for National Statistics (ONS) announced in the Census 2021 White Paper, Help Shape Our Future: The 2021 Census of Population and Housing in England and Wales (PDF, 968KB), that:
we will continue to work with the Valuation Office Agency (VOA) to explore the feasibility of supplementing the census questions with administrative data on total number of rooms, floor space and property type
we recommend that the census does not have questions on the number of rooms in each household because we intend to use alternative sources for this data
we are working with tax and benefits data from the Department for Work and Pensions (DWP) and Her Majesty's Revenue and Customs (HMRC) to develop census-type income data that can be integrated with the data collected in Census 2021
Updates for these commitments are provided on this page.
Valuation Office Agency property type
Our research has shown that administrative data from the Valuation Office Agency (VOA) have the potential to remove the need for us to collect property type information via a census or surveys. This type of data from the VOA can also provide new breakdowns of property types not available from a census or surveys. This may help meet user needs for more detailed categories of property type. For example, new analysis could include being able to distinguish between bungalows, houses and different types of terraced houses.
However, we need further research to establish if administrative data can provide comparable information with the census accommodation type for dwellings "above or within commercial buildings". Additional research will also help us understand how to address the small proportion of records where VOA property type and census accommodation type appear contradictory.
At this point, the ONS does not intend to use either VOA property type as part of Census 2021.
Valuation Office Agency floor space
Administrative data from the Valuation Office Agency (VOA) also offer the opportunity for additional insight into understanding living conditions in England and Wales by providing information on floor space. This information could be used to provide alternative overcrowding measures that focus on living space available (per person) instead of just looking at the number of rooms or bedrooms.
Our analysis found that floor space generally follows the expected distribution by property type. However, floor space is measured using two methods depending on the property type. This allows us to compare floor space for properties of the same type, but we need to be cautious when comparing floor spaces measured by differing methods.
At this point, the ONS does not intend to use either VOA floor space type as part of Census 2021.
Valuation Office Agency number of rooms
A Census 2021 topic consultation found that:
more respondents used number of bedrooms than number of rooms
number of rooms primarily meets the same information need as number of bedrooms, which is for under- and over-occupancy
the data quality for a question on number of bedrooms is greater than for a question on the number of rooms - the 2011 Census Quality Survey (CQS) (PDF, 1.4MB) measured 91% agreement for number of bedrooms compared with 67% for number of rooms and found that differences occurred because respondents had misunderstood the question
In 2017, we looked at the potential of using Valuation Office Agency (VOA) data as an alternative to estimating the number of rooms and bedrooms on Census 2021. We found that the direct agreement rate between the 2011 Census and VOA data for number of rooms was 16%. This was primarily attributable to differences in definitions between the 2011 Census and VOA.
The census included kitchens, utility rooms and conservatories in its number of rooms estimates, which the VOA does not. Since most properties have a kitchen, the number of rooms recorded in the census data was generally higher than the corresponding number of rooms in the VOA data. If we assume that the number of rooms derived using VOA data records is at least one room less than the census then the agreement rate increases to 48%.
Comparatively, the quality of the census responses for number of rooms was measured by the 2011 Census Quality Survey (CQS) (PDF, 1.4MB) at 67%. The survey found that differences occurred because respondents had misunderstood the question. Most of these differences (93%) were within plus or minus one room.
Given these findings and the ONS's intention to reduce respondent burden, the Census 2021 White Paper has recommended keeping the number of bedrooms question. It also suggested replacing the number of rooms question by using an alternative data source.
Using the VOA number of rooms for Census 2021 does imply a discontinuity with 2011 Census estimates, because of the definitional difference, which users need to be aware of. It will not be appropriate to measure change in number of rooms from 2011 to 2021 and, instead, we can use the census bedroom question for comparisons over time. The VOA number of rooms for Census 2021 will provide a high-quality relative measure of size, for example enabling the comparison of households across areas within the same time period.
In July 2020, we published a summary paper and methodology paper that provide an overview of how we plan to address missing values when replacing the number of rooms question in Census 2021. We also published a quality assessment of administrative data for the use of VOA data in Census 2021 to provide further assurances to our users.
In January 2021, we published an article that looks at the impact the use of VOA number of rooms in the 2021 Census has on room occupancy ratings, outlining the method we plan to use to account for definitional differences.
We are aware of the great interest in income data and the value that this could provide in planning, policy development and evaluation.
The Office for National Statistics (ONS) has been working with tax and benefits data from the Department for Work and Pensions (DWP) and Her Majesty's Revenue and Customs (HMRC) to develop small-area income data that can be linked with the data collected in Census 2021. These additional components depend on having timely access to underlying data sources and overcoming the complexity in combining data from different sources.
The ONS has already produced some research outputs, Admin-based income statistics (ABIS), to demonstrate the potential of this approach. We're continuing to develop these research outputs and published our latest set of experimental statistics on small area income distributions in June 2021. These statistics were the first to incorporate self-employment income. We currently plan to publish a further update in 2022. We intend to use these publications to gather user feedback on our administrative-data based income measure and additional user requirements.
We've also developed a methodology working paper on imputation methods for an administrative-based income measure linked to census data. We're considering when we will be able to publish these outputs.
You can find more information about all our plans for progressing a programme of work to put administrative data at the core of population, migration and social statistics.
If you have any questions about our integrated outputs, you can email us at firstname.lastname@example.org with your queries.