FOI Ref: FOI/2022/4667
You asked
Please advise:
1. Which towns/areas/streets in Hampshire were NOT included in the 2021 census ?
2. How many addresses do ONS accept may not have been covered in England in the 2021 census exercise ?
We said
Thank you for your request.
The design of Census 2021 aimed to invite all residential addresses in England and Wales to respond. For the design to be implemented successfully, ONS set a quality target of identifying 99.25% of residential addresses (no more than 0.75% under-coverage).
Our initial address frame included more than 27 million household address records and was based on data from AddressBase Premium which is widely used across both the public and private sector and is continually updated by Geoplace. It uses Local Land and Property Gazetteers (LLPGs) in conjunction with a range of address intelligence sources such as from the Valuation Office Agency (VOA), Royal Mail and Ordnance Survey.
In addition to our initial frame, we worked with GeoPlace to continually update our address lists up to, and including, Census Day (21 March 2021). We also provided several channels through which we encouraged the public to contact us if they had not received an invitation to complete their Census form, and updated our records -- where necessary -- based on information provided by respondents.
To enable population counts to be produced that provide statistically robust estimates, we also conducted a follow-up Census Coverage Survey (CCS) across a sample of England and Wales, which was operationally independent from Census 2021. The CCS was used to adjust for under-enumeration at the national, local and small area level, and included an independent address listing exercise.
In answer to your specific queries:
No towns, areas or streets in Hampshire were not included in Census 2021, as far as ONS is aware.
Based on our estimates, our original address frame (therefore not including addresses that were added during collection for Census 2021) had under-coverage of addresses of 0.36%. This was well within the quality target we had for under-coverage nationally of 0.75%.