The census 1911-1931 In the 20th century, both technological and social developments brought change to the census. Mechanical sorting was introduced in time for the 1911 census. The same census also saw the introduction of a question about the fertility of marriage - prompted by the concern about falling birth rates - and a distinction between occupation and industry. This latter innovation, which was repeated in 1921, not only produced more accurate results, but allowed new theories about social class to develop. In 1921 people were asked about their education and how they travelled to work. In 1931, however, the onset of widespread economic depression reduced the scope of the census, and the questions that had been introduced in 1911 and 1921 were dropped.
		The census 1951-2001
(49k)	The outbreak of war in 1939 meant that no census was taken in 1941, but peacetime - and the spirit of confidence it engendered - prompted another expansion in 1951. Questions regarding place of work, educational standards, fertility and household amenities were introduced. This broadening of scope has continued to characterise each subsequent census, reflecting how society is changing. Recent examples of this include a question about educational and professional qualifications (1961); how many cars and vans each household owns (1981); and an assessment of an individual's health (2001).

The other major change to the census in the post-war period has been in the method of analysing the data. Computers were used for the first time in 1961 and, although it took about the same length of time to process the information, twice the amount of results were produced. Significant advances in technology have considerably speeded up the process and the Office for National Statistics (ONS) forecast, for the 2001 census, that they would be able to produce over two billion individual statistics from the information they received in April 2001. Using the census after 1901 Although statistical analysis from each census is published, data on individuals is closed to the public for 100 years. This means that the latest one for which historians can see these details is the 1901 census. The census for 1911 will be opened to the public on the first working day of 2012.