Population microdata (survey data) comprise a list of individuals, normally nested into families and households, with each individual having an associated set of personal demographic and socio-economic characteristics.  However, to protect respondent confidentiality, publicly available population microdata are typically stripped of all sub-regional geography. 

In response to this data shortfall, a UK-wide set of spatially-detailed synthetic population microdata is now being created, initially based on the smallest output areas used in the 1991 UK Census.  These estimates are freely available to all those registered as users of the 1991 Census Sample of Anonymised Records (http://www.ccsr.ac.uk/ccsr/sars).  Assessments of the goodness-of-fit of the synthetic microdata created for each small-area in the UK are publicly available without registration.

There are two main alternative approaches to creating synthetic small-area microdata: synthetic reconstruction and combinatorial optimisation.  A thorough assessment of the statistical reliability of both approaches has been undertaken (see Huang and Williamson, 2001 ).  The preferred approach is combinatorial optimisation.

A by-product of research into the creation of synthetic population microdata has been an insight into the nature of differences between places, and the derivation of an improved correction for the Index of Dissimilarity when used in situations involving small counts (see End of Award Report for details)