The one-number census approach was developed by the Office for National Statistics to adjust the counts from the 2001 census of England and Wales for underenumeration. The method is underpinned by an assumption of independence between the count of the population that was given by the 2001 census...

The 2001 UK census was a one-number census. An integral part of such a process has been the creation of a transparent census database that has been adjusted for the underenumeration in the 2001 census. The methodology for creating this database is based on a controlled donor imputation system...