Metadata differences in Census 2021 between ONS and Nomis

ONS and Nomis use different systems to hold and process Census data. This can mean that for certain datasets it is necessary to alter the metadata slightly between the two websites.

There are two main reasons why this would be the case:

  1. Sometimes Census datasets only apply to subsets of the population. This means that the dataset population can be different on Nomis compared to the ONS website due to the way we handle the 'does not apply' populations.

    • For example, the question on unpaid care was only asked of people aged 5 years and over. The unpaid care dataset (TS039) has a 'does not apply' category on the ONS website which represents the population aged 0-4 years. The dataset population is therefore 'All usual residents' because people of all ages are represented in the data.
    • On Nomis however the 'does not apply' category is not included, therefore the dataset population has been changed to 'All usual residents aged 5 and over'.
  2. Sometimes we have had to shorten or rearrange category labels for presentational purposes on Nomis.

    • For example, on Nomis we have shortened the category labels on the highest level of qualification dataset (TS067). On the ONS version of the dataset one category is:
      'Level 1 and entry level qualifications: 1 to 4 GCSEs grade A* to C, Any GCSEs at other grades, O levels or CSEs (any grades), 1 AS level, NVQ level 1, Foundation GNVQ, Basic or Essential Skills'
    • On Nomis it is the shorter:
      'Level 1 and entry level qualifications'.

It's important to note that the underlying values are exactly the same across ONS and Nomis datasets. Our policy is to make as few changes as needed to ensure consistency across both websites.

For further details on any specific changes, please contact ONS Census Customer Services.