[4] A total of 81,000 field staff were employed across the UK (70,000 in England and Wales, 8,000 in Scotland and 3,000 in Northern Ireland).

[6][7] The census was estimated to cost £259m over its 13-year cycle from the start of planning in 1993 to the delivery of final results in 2006.

The forms were then pulped and recycled, and the digital copies printed onto microfilm for storage and release after 100 years.

Once the data were returned to the statistics agencies it underwent further processing to ensure consistency and to impute missing values.

[11] The results still represent 100 per cent of the population, however, because some individuals not completing their forms were instead identified by census enumerators, and through the use of cross-matching with a follow-up survey.

[17] This was an attempt to adjust the census counts and impute answers to allow for estimated under-enumeration measured by the Census Coverage Survey (sample size 320,000 households), resulting in a single set of population estimates.

[19][20] The inclusion of the question enabled the Jedi census phenomenon to take place in the United Kingdom.

Since the UK census relies on self-completion,[23] the composition of the other ethnic group category is not fixed.

[26][27] It is sometimes claimed that the 2001 census revealed that two-thirds of the population of Wales described themselves as of Welsh nationality.

[6][28] For the first time in a UK census, those wishing to describe their ethnicity as Cornish were given their own code number (06) on the 2001 UK census form, alongside those for people wishing to describe themselves as English, Welsh, Irish or Scottish.