Census 2021

  • By Mary-Ann Domman

The Office for National Statistics (ONS) is undertaking the next decennial Census in England and Wales on Sunday 21 March 2021. This briefing provides an overview of the Census and its importance, and outlines preparations London boroughs can start making to support a high response rate, to ensure that reliable, high quality information about our residents, housing, businesses and workers is collected.


The Census has run every 10 years since 1801 to gather information from every household and individual across the United Kingdom. It collects a large amount of information on the demographics of residents (such as age, gender, ethnicity, religion, sexual orientation, health, living arrangements), their housing, mode of travel to work and employment. Census data provides some information that is not available elsewhere and at a level of detail that is not obtainable from other government surveys – information is available about small population groups, and for small geographic areas. It is currently the gold standard of data and will be used to re-calibrate population estimates for the next 10-year period.

Why is it important?

The Census is not just a headcount, it is vital in making informed policy decisions by providing accurate information on local demographics, housing, employment and need. The information it collects helps with decisions on the planning and funding of council run services in local areas, along with where social care, schools, doctors’ surgeries and emergency services are needed most. Accurate population figures and detailed information about people are also important in determining the funding of key public services, as well as for the voluntary and community sector and businesses.

London’s low response rate

London has the lowest response rate of all regions and contains most of the lowest responding authorities in England. In London historically only 9/10 people fill in the Census questionnaire, even though it is a legal requirement to do so. The issues persist, as the 2019 Census dress rehearsal response rates for London areas remained much lower than elsewhere.

There are lots of reasons for this, including language barriers, physical barriers to receiving or completing forms, or those unwilling to respond, which are outlined further below:

  • Migration – London is a world city and attracts people from around the globe. Around one in three Londoners were born overseas, compared with one in seven in the rest of the country1. These higher levels of migration mean, generally, London has a more transient population than other areas. Lack of familiarity with the Census and understanding of its importance, both contribute to low response rates.
  • Language barriers – 300 languages are spoken in the capital. Less than half the children in London schools are reported as having English as a first language (falling as low as 31 percent in Newham)2.
  • Household structures – London has a high concentration of households with hard-to-count characteristics, such as houses in multiple occupation (HMO), split properties and large households.
  • Homelessness – some people may not receive, or complete, a form due to their temporary circumstances and this could lead to missed ‘concealed’ households, who may have the greatest needs. Everyone at the address should be included on the form, this is our best opportunity to evidence need.
  • Housing – the prevalence of gated buildings, student halls of residence and properties with push-button access pose a challenge for the delivery of Census forms and follow up using face-to-face methods.

To compensate for these low response rates, the ONS assigns characteristics to people it has no information about. However, the groups with the highest levels of need tend to have the lowest response rates, meaning that London could once again be hit by a double whammy, as the people undercounted in the Census are precisely those more likely to need local authority support. Estimating the characteristics of these missing populations cannot be a substitute for counting them in the first place, especially when so much is at stake.

Cost of getting it wrong

The Census is the starting point for the population estimates and projections produced by ONS, which are in turn used to allocate billions of pounds of funding and inform the service planning decisions of local councils. Nearly all the major funding grants London’s local authorities receive depend on population statistics. For some, population is the most important variable, and for nearly all, they include formulae which rely on demographic and socioeconomic characteristics that are derived from the Census, such as age, ethnicity, qualification levels, living arrangements, employment and health status.

In 2020/21, prior to Covid-19, London boroughs received almost £13 billion in general and specific grants to fund local services (including the Dedicated Schools Grant which funds education services). London’s estimated population is now just over 9 million, meaning for every undercounted person, up to £1,430 could be lost in funding. A relatively small undercount of 10,000 people in London (0.1 per cent) could amount to £143 million over the next 10 years - equating to funding for an additional 410 social workers3.

Why is the 2021 Census different?

This may be the last full count of population in this way, with only administrative data providing estimates in the future. If this is the last full count it is imperative that it be as accurate as possible to ensure future estimates are based on reliable data.

The 2021 Census will be mainly online for the first time with a target of 75 per cent online. Most people will get a letter with a unique access code on it through the post, so they can enter the code into the Census website and fill in the questionnaire. A range of assistance will be made available to encourage online completion by the ONS, which manages the Census process. This includes a dedicated Contact Centre, work with community groups and field staff. Recruitment for 30,000 Census roles across England and Wales has already started, providing local temporary employment opportunities.


There will be communications plans from the ONS, the GLA, London Councils and locally about the Census ramping up from now onwards. Working with community leaders and local residents now, can help build understanding, eliminate misinformation and ensure the provision of necessary resources to drive up response rates in London’s under-represented communities.

Local works best

Local support around communication and support to complete the forms works best as it is targeted to those who need it most, from a trusted source and provided locally where it is needed. ONS is providing guidance, materials and information about the hard to count groups and key messages for areas, along with some specialist support for these groups, to supplement local knowledge and expertise. Census Support Centres will provide face to face help for those who are willing to go online to do their Census but lack the confidence, technology or skills to do so. Completion activities will run with community groups for those with concerns or language barriers, in known places.

Data collection is secure and confidential

Published statistics from the Census are completely anonymous, so no personal information is published. Census records are kept secure for 100 years and only then can they be seen by future generations. The ONS, which manages the Census has a strict security regime that follows government standards, including physical and IT security measures to protect data collected.


The Census will be run in March 2021, in Scotland and Ireland the Census has been delayed until March 2022. ONS will be reviewing plans for collection, delivery and face-to-face interactions depending on the Covid-19 levels at the time.

What London borough members can do:

  • Speak to your Census Liaisons in your borough who should now be in post. They will have information about the hard to count populations locally and local plans for Census engagement.
  • Speak to local people and community leaders about the importance of filling in the Census. Explain and stop the spread of misinformation.
  • Ask the community what local support they will need – translation, access to IT, help to complete the forms.
  • Key information to share:
  • It is easier to complete the Census online so others don’t see your personal information, if you want to complete a separate form from the rest of the household, or if you are in a household of six or more you don’t need to request a continuation form.
  • Personal information is necessary to help provide the right resources locally, not target or identify people.
  • Information is safe and cannot be accessed without a court order – it cannot be used to identify individuals or households.
  • How much funding is lost locally if people are not counted (up to £1,430 per person per year).
  • It only takes 20 mins to complete online for a household, less for an individual.


The Census is important because it influences the level of funding provided to a local authority. It also provides a wide range of information about the people, housing and employment in the local area that supports evidence-based policy development and the planning, delivery and monitoring of local services.

The 2021 Census is different and marks an important shift to going digital. This may be the last Census of its kind, as there is a strong push from government to use administrative data to provide the information collected instead. The Census Transformation Programme4 is exploring the administrative data sources and how this could be achieved. Therefore, it is vital that this Census is as accurate as possible to act as a comparator to these future administrative data sets.

Following a decade of funding cuts and the ongoing financial impact of Covid-19, London boroughs will be financially stretched for the next few years. It is vital that accurate numbers are collected, and boroughs can work with the GLA and ONS to do this.

We aim to provide a further briefing in early 2021 with additional information on upcoming key dates, what actions to take and when to expect local information.

Mary-Ann Domman, Principal Policy Analyst