1. Executive summary

In December 2018, the government presented to Parliament a White Paper Help Shape our Future: The 2021 Census of Population and Housing in England and Wales. This outlined the Office for National Statistics's (ONS's) proposal to collect information on housing to meet the needs for planning, decision-making and resource allocation for future housing needs and public services. At the local area level, the census is currently the only source of nationally comparable information on housing and is used widely in developing local plans and housing projections.

We will be asking questions on the same topics as the 2011 Census on housing for Census 2021, with the exception of number of rooms, which will not be asked. We will collect housing data in a way that is consistent with previous censuses.

The questions used to collect data on the topic of housing are:

  • type and self-containment of accommodation
  • number of bedrooms
  • type of central heating
  • tenure and type of landlord
  • number of cars or vans

Census 2021 will be an online-first census, with a target of 75% online returns. We have reviewed and tested each question online and have recommended additional design and functionality amends specific to the electronic questionnaire. We have also recommended additional changes to the question designs following our stakeholder engagement, evaluation and testing programmes. These changes will be detailed in this report.

The main recommended changes to questions designs are:

  • to remove the number of rooms question
  • to add and update the response options to the type of central heating question to better meet users' needs for these data
  • to add a response option to the type of accommodation question to better meet users' needs for these data
  • to add a response option to the number of cars or vans question to improve data quality
  • to re-design the self-containment question to improve the quality of data captured and reduce burden for respondents
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2. Aim of question development report

This report provides links to previously published research and the findings of additional testing that led to the final recommended questions for Census 2021 in England and Wales. The questions and response options for Census 2021 have now been finalised through the census secondary legislation: The Census (England and Wales) Order 2020 and Census Regulations for England and for Wales.

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3. Research and development timeline

In June 2015, the Office for National Statistics (ONS) held a formal, 12-week consultation process asking census users for their views on the topics that were required in the questionnaire in England and Wales. The aim of the consultation was to promote discussion and encourage the development of strong cases for topics to be included in Census 2021.

In May 2016, the ONS published its response to the 2021 Census topic consultation. This set out our updated view on the topics to be included in Census 2021, including:

  • a summary of proposals for new topics
  • next steps
  • an overview of our plans

A detailed summary of the consultation responses relating to the topic of housing can be found in the housing topic report (PDF, 1.7MB). In this report, the ONS made clear commitments to the public to:

  • investigate the impact that asking one question on number of rooms or number of bedrooms would have on acceptability and outputs

  • investigate using Valuation Office Agency (VOA) data as an alternative to asking questions on number of rooms or bedrooms

  • work with stakeholders to review the responses to the "type of central heating" question

  • continue to collect information on all other housing topics

We have provided an update on how we met these commitments in Annex 1.

Following this, we began a comprehensive programme of research and development. A full list of the tests used in the development of the questions on housing is shown in Annex 2. Further details are provided in the Summary of testing for Census 2021.

The tests utilised a range of qualitative and quantitative research methods. A short description of the different research methods and sampling techniques is given in the Question and questionnaire development overview for Census 2021. Testing included participants living in varied accommodation and from a wide range of backgrounds.

In December 2018, the government presented to Parliament a White Paper Help Shape our Future: The 2021 Census of Population and Housing in England and Wales. This outlined our proposal to collect information on the topic of housing and stated our recommendation not to collect data on number of rooms. Further information can be found in Annex 1.

The question recommendations for Census 2021 are now finalised. We have evaluated the questions for their potential impact on data quality, public acceptability, respondent burden, financial concerns and questionnaire mode. We have presented details of this evaluation in Annex 3.

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4. Research that led to the 2018 White Paper recommendations

As set out in the White Paper Help Shape our Future: The 2021 Census of Population and Housing in England and Wales, we recommended that the census does not include a question on number of rooms. We would investigate the use of alternative sources for these data.

Number of rooms and number of bedrooms

A question on the number of rooms in a dwelling has been asked on the census since 1891. The data allow users to derive measures of under- and over-occupancy. A question on the number of bedrooms in a dwelling was asked for the first time in the 2011 Census, as this was a new measure of overcrowding introduced by the government. The question on number of rooms referenced the question on number of rooms, so the two questions had to be shown together.

2011 Census question

How many rooms are available for use only by this household?

Do NOT count:

  • bathrooms
  • toilets
  • halls or landings
  • rooms that can only be used for storage such as cupboards

Count all other rooms, for example:

  • kitchens
  • living rooms
  • utility rooms
  • bedrooms
  • studies
  • conservatories

If two rooms have been converted into one, count them as one room

(Write in) Number of rooms

How many of these rooms are bedrooms? Include all rooms built or converted for use as bedrooms, even if they are not currently used as bedrooms

(Write in) Number of bedrooms

Redesigning the number of bedrooms question

Following the consultation, we removed the number of rooms question and redesigned the number of bedrooms question as an independent question. We tested (2018:35) the new question both with and without the instruction.

How many bedrooms are available for use only by this household? Include all rooms built or converted for use as bedrooms, even if they are not currently used as bedrooms

(Write in) Number of bedrooms

Feedback from testing

All respondents answered the question correctly with or without the instruction. The new question stem included the phrase "available for use", which respondents found helpful and correctly included how many bedrooms that were officially converted or not.

Respondent feedback led to the recommendation to include the first part of the instruction, as this clarified what to do if room conversions had occurred, and not to include the second part of the instruction, as respondents understood this through reading the question and first part of the instruction.

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7. Next steps

In July 2020, we published a summary 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. We will conduct further analysis to ensure we are operationally ready for Census 2021, and to provide further assurance for the replacement of the number of rooms question in Census 2021. Our next publication will explore differences in occupancy ratings derived from Census 2011 and linked Valuation Office Agency number of rooms data.

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8. Annex 1: Census commitments made on the topic of housing

In the Census 2021 topic consultation response, the Office for National Statistics (ONS) committed to continuing to ask questions on the housing topic and develop these for online. We made three further commitments related to housing.

Explore the impact of removing one of the questions about rooms in the household

In our response to the Census 2021 topic consultation (PDF, 1.7MB), we stated that we did not believe it was appropriate to ask two questions designed to meet a single information need if there is no clear requirement to do so. In this case, the data collected by both number of rooms and number of bedrooms were used to identify over- and under-occupancy.

The 2011 Census Quality Survey (PDF, 1.4MB) asked the same questions as the 2011 Census again to measure agreement between the two sources. If all respondents provided the same answers to the Census Quality Survey that they provided in their census return, then agreement would be 100%.

This identified that the quality of data was higher for the "number of bedrooms" question, with 91.4% agreement, compared with just 66.5% agreement for the "number of rooms" question. The findings indicated that the number of rooms question was not a source of reliable data, indicating respondents may include or exclude certain rooms when asked at different times.

We therefore revised and tested a standalone "number of bedrooms" question to ensure the data would continue to meet the user need for counting under- and over-occupancy as discussed in this report.

Explore the potential of using Valuation Office Agency data as an alternative source of information about number of rooms

In our response to the Census 2021 topic consultation (PDF, 1.7MB), we outlined our intention to investigate the use of Valuation Office Agency (VOA) data to provide information on number of rooms and bedrooms.

European Regulation (EC) No 763/2008 requires the ONS to provide census-derived statistics, or equivalent data, on number of rooms to Eurostat, cross-tabulated with a limited number of other sub-topics.

In March 2015, Parliament approved an Information Sharing Order to allow the VOA to share information about addresses with the ONS, including physical attributes, which covers the number of rooms.

Consultation on using Valuation Office Agency data

In June 2017, we published Estimating the number of rooms and bedrooms in the 2021 Census: An alternative approach using VOA data. This research looked at VOA data as a potential alternative source for estimating the number of rooms and bedrooms.

We then held a public consultation from 28 June to 25 September 2017, inviting users to respond to this publication.

The consultation revealed that data users were able to calculate under- and over-occupancy from either the number of rooms or the number of bedrooms question. More users relied on the data from the number of bedrooms question. We found no evidence that both questions were required on the census.

Respondents to the consultation highlighted several concerns with using VOA data rather than census data:

  • there was a significant difference between the 2011 Census and VOA data for the number of properties classified as over-occupied

  • there were concerns with how often the VOA data are updated

  • VOA records data at the address level and the census records data at the household level; respondents were unclear how this difference would impact data use

We concluded that relying on VOA data alone would likely impact data use and comparability with census data. Therefore, we will continue to ask the "number of bedrooms" question to derive data on under- and over-occupancy in Census 2021.

We will continue to work with VOA data to enhance outputs for Census 2021. Further research and an update on achieving this will be published in 2020.

2021 Census White Paper commitments

In the December 2018 White Paper Help Shape our Future: The 2021 Census of Population and Housing in England and Wales, we further committed to continue work with the VOA to explore the feasibility of supplementing the census questions with administrative data on total number of rooms, living space and property type. We have published research on the latter two. We do not propose including questions on living space or property type.

Engage with stakeholders to explore requirements for the type of central heating question and ensure it fully meets user needs

We worked with various stakeholders to update the list of response options to the type of central heating question, including the Department of Energy and Climate Change, the Welsh Government, and local authorities. The final list of response options was designed to meet the data needs of these stakeholders.

Recommended Census 2021 response options that were tested, and the findings of testing, are discussed in more detail throughout this report. The examples of central heating types that are shown alongside the response options were provided by the Department for Business, Energy and Industrial Strategy (BEIS).

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9. Annex 2: Summary of research undertaken for the topic of housing, 2016 to 2020

References to tests take the form (Year: Test number). "Year" refers to the calendar year the test was undertaken in, and the test number is the position of the test within the year considering all testing that took place in that year. For example, the fifth test conducted in 2017 would be referenced as (2017:5).

A full description of each of these items can be found in Summary of testing for Census 2021.

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10. Annex 3: Question evaluation

Evaluation of the type of accommodation question

The type of accommodation question has been assessed as having a "Low" potential for impact on data quality, public acceptability, respondent burden and financial concerns.

Potential for impact on questionnaire mode: "Medium"

On the electronic questionnaire, type of accommodation was split into a two-stage question to reduce the need for scrolling on a mobile device, in line with the Government Digital Service's Service Standard. The electronic questionnaire contains "address piping" functionality to improve the respondent journey through this question, which is not viable on the paper questionnaire.

Evaluation of the self-containment of accommodation question

The self-containment of accommodation question has been assessed as having a "Low" potential for impact on data quality, public acceptability, financial concerns and questionnaire mode.

Potential for impact on Respondent Burden: "Medium"

The self-containment of accommodation question has a long question stem of over 20 words. In the 2019 Rehearsal, respondents spent a longer time on this question (14 seconds) than on the evaluation threshold (10 seconds).

Evaluation of the number of bedrooms question

The number of bedrooms question has been assessed as having a "Low" potential for impact on all five assessment criteria: data quality, public acceptability, respondent burden, financial concerns and questionnaire mode.

Evaluation of the type of central heating question

The type of central heating question has been assessed as having a "Low" potential for impact on public acceptability, financial concerns and questionnaire mode.

Potential for impact on data quality: "Medium"

The central heating question asks for information that cannot be observed in some cases. Testing, including the 2019 Rehearsal, has shown that some respondents have difficulty understanding the concept of central heating.

Potential for impact on respondent burden: "High"

The type of central heating question requires respondents to read the question stem and additional instructions. They must also read a list of 10 response options, with some examples, as this is a select all that apply question.

Evaluation of the tenure question

The tenure question has been assessed as having a "Low" potential for impact on public acceptability, respondent burden and financial concerns.

Potential for impact on data quality: "Medium"

The central heating question asks for information that cannot be observed in some cases. 2019 Rehearsal feedback showed that some respondents had difficulty in understanding this question.

Potential for impact on questionnaire mode: "Medium"

The tenure question on the electronic questionnaire has added functionality to improve the data collected by users and improve user experience of the questionnaire. These functionalities are "address piping" and validation forcing respondents to select a response option before they can continue to the next question.

Evaluation of the type of landlord question

The type of landlord question has been assessed as having a "Low" potential for impact on all five assessment criteria: data quality, public acceptability, respondent burden, financial concerns and questionnaire mode.

Evaluation of the number of cars and vans question

The number of cars and vans question has been assessed as having a "Low" potential for impact on all five assessment criteria: data quality, public acceptability, respondent burden, financial concerns and questionnaire mode.

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11. Annex 4: UK harmonisation of the housing topics

Throughout the development of the Census 2021 questionnaires, the Office for National Statistics (ONS), National Records of Scotland (NRS) and Northern Ireland Statistics and Research Agency (NISRA) have worked together to ensure harmonisation of the outputs from the housing questions where possible.

Based on the proposed designs, there are some important differences between UK statistical offices, resulting from differing data user needs.

Question design

Landlord

The Northern Ireland question stem "Who do you rent from?" differs from the England, Wales and Scotland question stem "Who is your landlord?". The response options regarding Housing associations, Council or local authorities in Northern Ireland, England and Wales, and Scotland all differ. Scotland have fewer response options on the landlord question compared with Northern Ireland, England and Wales.

Central heating

All three statistical offices ask the same question with the same instructions. However, the list of response options is different in each country.

In Northern Ireland only, there is a question on renewable energy systems.

Type of accommodation

Scotland and Northern Ireland differ in the type of accommodation question response option "in a purpose-built block of flats or tenement". Scotland uses "in a tenement or purpose-built block of flats (including '4-in-a-block')", while in Northern Ireland they use "in a purpose-build block of flats".

Tenure

In Scotland only, in the question on tenure, they have an extra response option that is "Owns with shared equity (for example, LIFT, Help-to-Buy)" because of differing user needs. Northern Ireland's response option order differs with "Owns with a mortgage or loan" being first.

Self-containment and number of bedrooms

In Scotland only, the self-containment question uses the 2011 Census design question stem, "Are all the rooms in this accommodation behind a door that only this household can use?" compared with the England and Wales question stem "Are all the rooms in this accommodation, including the kitchen, bathroom and toilet, behind a door that only this household can use?".

Scotland recommend using the 2011 Census design "No" response option, while England and Wales recommend "No, one or more rooms are shared with another household".

Northern Ireland do not ask questions on number of bedrooms or self-containment of accommodation.

Northern Ireland are using administrative data to gather date on number of bedrooms. There is less user need for a question on self-containment in Northern Ireland than in England and Wales and Scotland.

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