2011 UK Census coverage assessment and adjustment methodology

Every effort is made to ensure everyone is counted in a census. However, no census is perfect and some people are missed. This undercount does not usually occur uniformly across all geographical areas or across sub-groups of the population such as age and gender. Further, the measurement of small populations, one of the key reasons for carrying out a census, is becoming increasingly difficult. In terms of resource allocation, this is a big issue since the people that are missed can be those who attract higher levels of funding. Therefore money may be wrongly allocated if the Census is unadjusted. ONS outlined its coverage assessment and adjustment strategy in Population Trends 127 (see Abbott, 2007), noting where improvements over the methodology used in 2001 would be sought. This article outlines the proposed methodology for the 2011 Census arising from that strategy, and focuses on the research that has been conducted to date to develop those improvements and innovations.