Censuses past
The census for England and Wales is a survey of all households. Taken every 10 years, each household completes its own 'return', which includes any overnight visitors on the day itself.
Censuses are not new. England's first modern census was taken in 1801 - though 1841 was the first detailed survey.
At the time, information from the returns was handwritten by clerks into enumeration books. In 1911, punch cards were first used for processing the information and computers were introduced in 1961.
The data gathered has changed over time - from questions on flush toilets in 1951 to student accommodation in 1981. Reflecting a growing diversity, questions on ethnicity and religion have been added in the last 30 years.
To protect personal information, the census is closed to public access for 100 years - although statistics derived from it are available much sooner. Once opened, they are an invaluable tool for family historians, and can reveal much about social life in the past.