Until 1911 census information was processed entirely by hand, using nothing more than pen and paper and a small army of clerks. In 1911 punch cards and mechanical sorting were introduced and computers were first used in 1961.
Today the census forms are scanned in (creating an electronic image of the form), the data captured and written responses coded. As far as possible all of these operations are automated. The electronic image is then transferred to microfilm for archiving and for the first time in 2001 the paper forms were pulped and recycled.
Further information on this topic can be found in the Overview Unit on Methods
of Data Collection and Coding