Mismatches and matches in address information from the Census and the BSO: A longitudinal perspective 2001-2011

Accurate address information from health service providers is fundamental for the effective delivery of health care and population monitoring and screening. While it is currently used in the production of key statistics such as internal migration estimates, it will become even more important over time with the 2021 Census of UK constituent countries integrating administrative data to enhance the quality of statistical outputs. Therefore, it is beneficial to improve understanding of the accuracy of address information held by health service providers and factors that influence this. This paper builds upon previous research on the social geography of address mismatch between census and health service records in Northern Ireland. It is based on the Northern Ireland Longitudinal Study; this is a large data linkage study including about 28 per cent of the Northern Ireland population, which is matched between the census (2001, 2011) and Health Card Registration System maintained by the Health and Social Care Business Service Organisation (BSO). This research compares address information from the Spring 2011 BSO download (Unique Property Reference Number, Super Output Area) with comparable geographic information from the 2011 Census. Multivariate and multilevel analyses are used to assess the individual and ecological determinants of match/mismatch between geographical information in both data sources to determine if the characteristics of the associated people and places are the same as the position observed in 2001. It is important to understand if the same people are being inaccurately geographically referenced in both Census years or if the situation is more variable.