The UK census is an enumeration of the population conducted every ten years since 1801. The first four censuses involved only a count of the number of people residing in each household; but from 1841 onwards the amount of detail required has increased, to include age, gender, marital status, occupation, place of origin, etc. Censuses are therefore useful sources of historical information, but because of the personal data involved cannot be consulted for 100 years. The most recent census available for public examination is therefore that of 1901.