We recently had an enquiry about how we were able to show Census 2021 values for parishes when the Office for National Statistics (ONS) had not yet published them. The answer is that we aggregate values from smaller areas (in this case from Output Areas) to get an approximate value for each parish.

To help you see how we have done this, you can use our derivation functionality to show how we arrive at a value. For example, this Data Tool query (needs sign in or an API key) shows Census 2021 ethnicity breakdowns for each parish in Hampshire.

The Include derivation link checkbox is checked, so each value has a hyperlink to a popup explaining its derivation. You can also switch on derivation links in report tables and text token.

The degree of fit given in the above example says how closely the smaller areas used for aggregation fit into the area reported.

We used a similar aggregation approach to derive Census 2021 values for wards but overwrote those with native values when they were published by ONS on 30 January 2023.

For more information contact us: support@lginform.local.gov.uk.