Census 2021 main language responses

FOI reference: FOI-2025-3335

You asked

I am writing to request information under the Freedom of Information Act 2000 relating to the 2021 Census (England and Wales) question on "Main language".

The published tables include 95 language categories. I would like to obtain the full set of responses recorded through the write-in option "Other, write in (including British Sign Language)", together with information that shows how those write-in responses were processed and classified. 

In particular, I request the complete list of distinct write-in response strings as captured (i.e., the literal text as entered), and the frequency count for each distinct response. I also request the documentation and/or lookup resources used to standardise and code these write-in responses into separate languages (for example, any coding frames, codebooks, decision rules, or guidance used by coders or automated systems). Finally, I request the mapping showing how the standardised/coded languages derived from the write-ins were grouped into the 95 published language categories in TS024, including any category labels or codes used internally.

We said

Thank you for your request. 

Unfortunately, it would not be possible for us to disclose the requested full list of all write-in responses for Main-language in the 2021 Census due to the disproportionate time involved in prepping the material for disclosure.  

The character capacity for this question was 18 for paper forms and 100 for digital, which provides scope for respondents to write various additional information. Each response would need to be thoroughly reviewed to ensure that no personal data are included. This would involve a manual check of at least 3,400,000 rows of data. The cost limit for FOI compliance is 24 working hours, and this would be greatly exceeded if we were to action this request.  

Unfortunately, we do not see how we can offer a suitable suggestion for a reduction of scope. However, we are able to supply some similar information, which we hope will be useful for your purposes. 

For details on how original write-in responses are coded into categories, please refer to Section 6.2.3 of the Census 2021 General Report. 

The associated download provides a list of the 551 Main Language categories the raw information was coded into (MAIN_LANGUAGE_FLAT) and the 95 categories the flat figures were subsequently coded into (MAIN_LANGUAGE_DETAILED). 

We have produced an output showing how these code categories relate to one another along with a response count for each 551 categories, which we hope will be helpful for you. This can be accessed as an ad hoc on the ONS website. 

If you have any more questions about how our data are coded, please get in touch with us at Census.Customer.Services@ons.gov.uk.