The Carstairs index is an index of deprivation used in

spatial epidemiology Spatial epidemiology is a subfield of epidemiology focused on the study of the spatial distribution of health outcomes; it is closely related to health geography. Specifically, spatial epidemiology is concerned with the description and examinatio ...

to identify Socio-economic

confounding In statistics, a confounder (also confounding variable, confounding factor, extraneous determinant or lurking variable) is a variable that influences both the dependent variable and independent variable, causing a spurious association. Con ...

. The index was developed by Vera Carstairs and

Russell Morris Russell Norman Morris (born 31 July 1948) is an Australian singer-songwriter and guitarist who had five Australian Top 10 singles during the late 1960s and early 1970s. On 1 July 2008, the Australian Recording Industry Association (ARIA) recog ...

, and published in 1991 as ''Deprivation and Health in Scotland''. The work focusses on Scotland, and was an alternative to the

Townsend Index The Townsend index is a measure of material deprivation within a population. It was first described by sociologist Peter Townsend in 1988. The measure incorporates four variables: *Unemployment (as a percentage of those aged 16 and over who are e ...

of deprivation to avoid the use of households as denominators. The Carstairs index is based on four Census variables: low social class, lack of car ownership, overcrowding and male unemployment and the overall index reflects the material deprivation of an area, in relation to the rest of Scotland. Carstairs indices are calculated at the postcode sector level, with average population sizes of approximately 5,000 persons. The Carstairs index makes use of data collected at the Census to calculate the relative deprivation of an area, therefore there have been four versions: 1981, 1991, 2001 and 2011. The Carstairs indices are routinely produced and published by the MRC/CSO Social and Public Health Sciences Unit at the University of Glasgow. __TOC__

Calculating the Index

The components of the Carstairs score are unweighted, and so to ensure that they all have equal influence over the final score, each variable is standardised to have a population-weighted mean of zero, and a variance of one, using the

z-score In statistics, the standard score is the number of standard deviations by which the value of a raw score (i.e., an observed value or data point) is above or below the mean value of what is being observed or measured. Raw scores above the me ...

method. The Carstairs index for each area is the sum of the standardised values of the components. Indices may be positive or negative, with negative scores indicating that the area has a lower level of deprivation, and positive scores suggesting the area has a relatively higher level of deprivation. The indices are typically ordered from lowest to highest, and grouped into population quintiles. In the 1981, 1991 and 2001 indices, quintile 1 represented the least deprived areas, and quintile 5 represented the most deprived. In 2011, the order was reversed, in line with the ordering of the

Scottish Index of Multiple Deprivation The Scottish index of multiple deprivation (SIMD) is a statistical tool used by Local government in Scotland, local authorities, the Scottish government, the NHS Scotland, NHS and other government bodies in Scotland to support policy and decision m ...

Changes to the variables

The low social class component of the 1981 and 1991 Carstairs index was created using the Registrar General's Social Class (later Social Class for Occupation). In 2001, this was superseded by the National Statistics Socio-economic Classification (NS-SEC). This meant that the definition of low social class had to be amended to reflect the approximate operational categories. The definition of overcrowding was amended between 1981 and 1991, due to the inclusion of kitchens of at least 2 metres wide into the room count in the census.McLoone, P. (1994) Carstairs Scores for Scottish Postcode Sectors from the 1991 Census. Public Health Research Unit, University of Glasgow http://www.sphsu.mrc.ac.uk/files/File/library/other%20reports/Carstairs.pdf

References

{{Indices of Deprivation Epidemiology Social statistics data 1991 introductions