A population census has been taken every ten years since 1801, excluding 1941. Most of the early returns for 1801-1831 were unfortunately destroyed, although in some isolated instances they have been preserved. The early returns, where they have survived usually only name the householder and list the number of people in the house, although occasionally the whole population is listed.
The census returns for 1841 were the first to be kept and released by the Public Record Office after a hundred years, and the returns for 1841-1901 are now publicly available. The 1841 census was the first to record all personal names, although place of birth was not recorded, simply a Y or N as to whether they were born within the county. For those under the age of 14 the exact age is given, but the ages of those aged 15 or more are rounded down to the nearest 5 years below, eg someone who stated he was 23 would have been recorded as 20.
From the 1851 census onwards the place of birth and exact age stated is recorded.