How big is the 1921 Census?

The 1921 Census of England and Wales occupies 1.6 linear kilometres of shelving, holding details of just under 38 million people living in England & Wales in June 1921. The increase in population since 1911 was approximately 1.8 million, showing the impact of the First World War as this was only half the increase from 1901 to 1911, and proportionally the lowest increase recorded since the first census in 1801.

It comprises two sets of records:

Approximately 8.5 million householder questionnaires – or schedules (RG 15) held in 28,152 volumes, each comprising about 300 schedules. Each schedule is completed by each householder and is in the householder’s writing (some appear to have been completed by other members of the family).
1,992 volumes of Plans of Division (RG 114). Each Plan of Division is a standard 32-page booklet in which local registrars recorded how their registration subdistrict would be divided up into enumeration districts for the census. In urban areas, they list which streets are in which enumeration districts, and even which particular range of house numbers from a street fall into a given enumeration district. In rural areas, it indicates which hamlets and outlying farms were included in a particular enumeration district. Enumeration districts were designed so as possible such that a single enumerator could visit all the properties on census day to collect the schedules after completion.

The newly digitised version of the census:

Enables people to easily search the census records online from the comfort of their own home
Takes up 200 terabytes of computer storage using our preferred image format of JPEG2000, to store these images as TIFF files would take around 1.4 petabytes of storage.
Constitutes more than 20 million colour images - a 25 percent increase on the 1911 census.

We have worked with a trusted transcription house on numerous projects for several years. When transcription of the 1921 Census took place, each digital image had to be broken up into segments so that the person transcribing it could not see a whole record or household. This was to ensure we complied with security and data protection regulations but also why you might see various spellings of the same surname or street address on one record because it has been transcribed by multiple people without the context of the whole record
Our aim when working on the transcription of the 1921 Census was to deliver a 98.5% accuracy rate across the 38 million individual records and from our initial quality control we believe we have achieved this. However, due to the secure nature of the 1921 Census project, the period of time in which we have been able to access and review the data ahead of launch has been limited and we have been unable to conduct the same level of quality assurance checks we would normally apply to such a major release.
To ensure the highest possible transcription standards we will be continually reviewing the data to correct any and all errors over time.

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