The 1801 census returned information on numbers of households, individuals, occupations etc., but did't include names, addresses, relationships within households. The 1801 census for Amlwych in Anglesy is the exception to this rule and is very informative for anyone researching their Amlwych ancestors.
By 1841 additional information was added, names and occupations were recoded but not family relationships. It was only noted whether or not the individuals were born in the county where the census was taking place , this was recoded as yes or no. It was also noted whether they were born in Ireland, Scotland or Wales . This usually took the form of I, S or W for the latter countries.
After 1851a lot more information was added such as place f birth and relationship to head of household. In later census's in Ireland,Wales and Scotland languages were noted such as Welsh, Irish or Gaelic, in order to record the number of individuals who either did not speak English or who were bilingual.
There is a campaign in progress to try and get the 1911 census return released before the 100 year rule.