THE CORNISH CENSUSES
The first UK census began in 1801 and continued to be held every decade. The names and details of the early censuses from 1801 to 1831 were not kept. It was not until 1841 that names were preserved. As the decades passed the census were refined making these documents very useful and reliable tools for family history research.
The 1841 census used a rounding down to the nearest five years method when determining the age of a person. For example, if person was aged 31 it would be rounded down to 30 or if someone was aged 29 it would be rounded down to 25.