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), Ireland in 1921/Northern Ireland in 1931, and Scotland in 2021. 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 UK government. The most recent UK census took place in England, Wales and Northern Ireland on 21 March 2021. Because of the COVID-19 pandemic, the census in Scotland was delayed to 20 March 2022. History 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" (). The first census in England was the Domesday Book, compiled in 1086 under William the Conqueror 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: "the intimate knowledge of any country must form the rational basis of legislation and diplomacy" "an industrious population is the basic power and resource of any nation, and therefore its size needs to be known" "the number of men who were required for conscription to the militia in different areas should reflect the area's population" "there were defence reasons for wanting to know the number of seamen" "the need to plan the production of corn and thus to know the number of people who had to be fed" "a census would indicate the Government's intention to promote the public good", and "the life insurance industry would be stimulated by the results". Regular national censuses have taken place every ten years since 1801, most recently in 2021; other partial censuses have been made