Census in the United Kingdom

Coincident full censuses have taken place in the different jurisdictions of the United Kingdom every ten years since 1801, with the exceptions of 1941 (during the Second World War) and Ireland in 1921. Simultaneous censuses were taken in the Channel Islands and the Isle of Man, with the returns being archived with those of England. In addition to providing detailed information about national demographics, the results of the census play an important part in the calculation of resource allocation to regional and local service providers by the governments of both the UK and the European Union. The most recent UK census took place in 2011.

Tax assessments (known in the later Empire as the indiction) were made in Britain in Roman times, but detailed records have not survived. In the 7th century AD, Dál Riata (parts of what is now Scotland and Northern Ireland) conducted a census, called the "Tradition of the Men of Alba" (Scottish Gaelic: Senchus fer n-Alban). England conducted its first formal census when the Domesday Book was compiled in 1086 under William I for tax purposes.

Distinct from earlier, less inclusive censuses (e.g. for religious purposes), national decennial censuses of the general population started in 1801, championed by the statistician John Rickman. The censuses were initially conducted partly to ascertain the number of men able to fight in the Napoleonic Wars, and partly over population concerns stemming from the 1798 work An Essay on the Principle of Population by Reverend Thomas Robert Malthus. Rickman's twelve reasons – set out in 1798 and repeated in Parliamentary debates – for conducting a census of Great Britain included the following justifications:

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