Census in the United Kingdom in the context of "2011 UK Census"

The book An Essay on the Principle of Population was first published anonymously in 1798, but the author was soon identified as Thomas Robert Malthus. The book warned of future difficulties, on an interpretation of the population increasing in geometric progression (so as to double every 25 years) while food production increased in an arithmetic progression, which would leave a difference resulting in the want of food and famine, unless birth rates decreased.

While it was not the first book on population, Malthus's book fuelled debate about the size of the population in Britain and contributed to the passing of the Census Act 1800. This Act enabled the holding of a national census in England, Wales and Scotland, starting in 1801 and continuing every ten years to the present. The book's 6th edition (1826) was independently cited as a key influence by both Charles Darwin and Alfred Russel Wallace in developing the theory of natural selection.

A census of the population of the United Kingdom is taken every ten years. The 2011 census was held in all countries of the UK on 27 March 2011. It was the first UK census which could be completed online via the Internet. The Office for National Statistics (ONS) is responsible for the census in England and Wales, the General Register Office for Scotland (GROS) is responsible for the census in Scotland, and the Northern Ireland Statistics and Research Agency (NISRA) is responsible for the census in Northern Ireland.

The Office for National Statistics is the executive office of the UK Statistics Authority, a non-ministerial department formed in 2008 and which reports directly to Parliament. ONS is the UK Government's single largest statistical producer of independent statistics on the UK's economy and society, used to assist the planning and allocation of resources, policy-making and decision-making. ONS designs, manages and runs the census in England and Wales. In its capacity as the national statistics office for the United Kingdom, ONS also compiles and releases census tables for the United Kingdom when the data from England and Wales, Scotland and Northern Ireland are complete.

The demographics of England have been measured by the decennial national census since 1801, and are marked by centuries of population growth and urbanization. Due to the lack of authoritative contemporary sources, estimates of the population of England for dates prior to the first census in 1801 vary considerably. The population of England at the 2021 census was about 56,489,800.

The Census Act 1800 – also known as the Population Act 1800 – (41 Geo. 3. (G.B.) c. 15) was an act of the Parliament of Great Britain which enabled the first Census of England, Scotland and Wales to be undertaken. The census was carried out in 1801 and has been repeated almost every ten years thereafter. The 1801 census estimated the population of England and Wales to be 8.9 million, and that of Scotland was 1.6 million. Ireland was not included in the census until 1821.

The first census of England had been carried out by William I and published in the Domesday Book in 1086. Various other censuses had taken place, such as that in the sixteenth century, in which bishops were asked to count the communicants or number of families in their dioceses. In the latter part of the eighteenth century, there were several proposals for a Census Bill and a growing concern about the population of Britain and its demand for food, particularly fuelled by the publication in 1798 of Thomas Robert Malthus's An Essay on the Principle of Population. The Census Bill was presented to Parliament on 20 November 1800, passed on 3 December and received royal assent on 31 December. The first census was held on Tuesday 10 March 1801.

A nationwide census, known as Census 2001, was conducted in the United Kingdom on Sunday, 29 April 2001. This was the 20th UK census and recorded a resident population of 58,789,194.

The 2001 UK census was organised by the Office for National Statistics (ONS) in England and Wales, the General Register Office for Scotland (GROS) and the Northern Ireland Statistics and Research Agency (NISRA). Detailed results by region, council area, ward and output area are available from their respective websites.