The methodology for achieving a One Number Census in 2001

One of the major uses of the decennial UK census is to provide figures on which to rebase the annual population estimates. This base needs to take into account the level of underenumeration in the cen-sus. Traditionally this has been measured from data collected in a post-enumeration survey (PES) and (at the national level) through comparison with the estimate of the population based on the previous census. In the 1991 Census, although the level of underenumeration was not high (estimated at 2.2 per cent), it did not occur uniformly across all socio-demographic groups and parts of the country. There was also a significant difference between the survey-based estimate and that rolled forward from the previous census. Further investigation showed that the PES had failed to measure the level of underenumeration and its degree of variability adequately. Maximising coverage in the 2001 Census is a priority. A number of initiatives have been introduced to help achieve this, for example: 1. the Census forms have been redesigned to make them easier to complete; 2. population definitions for the Census have been reviewed; 3. postback of Census forms will be allowed for the first time; and 4. resources will be concentrated in areas where response rates are lowest