Scottish Index of Multiple Deprivation (SIMD)
SIMD is the Scottish Index of Multiple Deprivation. It is calculated for residential areas such as postcodes, and ranges from 0.94 to 89.89. (2012 version). By population fifths ranging from Least Deprived (Fifth fifth) to Most Deprived (First fifth) - the opposite method of numbering to that used in the 2004 and 2006 versions results, are as follows:
| Population Fifth | Least Deprived | Most Deprived | |||
| Fifth | 5 | 4 | 3 | 2 | 1 |
| Range | 0.94 to 7.94 | 7.94 to 13.67 | 13.67 to 20.97 | 20.98 to 33.81 | 33.81 to 89.89 |
| Mean Score | 5.17 | 10.82 | 16.96 | 26.47 | 48.78 |
The SIMD distribution therefore has a long tail and shows a positive skew. The mean value is 20.68 by postcode and the median (middle) is 15.89.
The SIMD score which was first used in developing ASSIGN was SIMD 2004, subsequently updated for this website to SIMD 2006. Version 1.4 of ASSIGN (website only) of April 2013 and Version 1.5 (website and offline versions) of October 2013 use SIMD 2012. Although there have been some changes to the score both in its derivation, and relative movements up and down, the range and mean values of SIMD 2012 are almost the same as those for SIMD 2004. Indeed the SIMD score correlates very highly with other older deprivation scores such as the Carstairs score. See Scottish Index of Multiple Deprivation (SIMD) for further information on SIMD.
In deriving the ASSIGN score, survey data from 1984-1995 were used with 20 years follow-up data collected since then. This was then related to SIMD, a recently derived deprivation score. SIMD was found to be very powerful in identifying that element of risk which is related to social status and not explained by conventional risk factors.
In the ASSIGN score software found on this website there is incorporated a 'lookup' table for SIMD scores from postcode. After reading in the postcode of residence of the person concerned it places the corresponding SIMD score for that postcode into the calculation of the ASSIGN score. The scoring application is provided both for ‘Calculate the risk for NHS clinical use’ and ‘Calculate the risk for ASSIGN visitors’ However, because there are no SIMD codes for postcodes or zipcodes outside Scotland, the visitor webpage allows you to enter an estimated SIMD value. The Framingham cardiovascular risk score provided for comparison in the visitor page does not utilize an index of social deprivation such as SIMD although it appears in the data entry field.
Version 1.4 of ASSIGN from April 2013 and Version 1.5 of October 2013 use SIMD 2012 where earlier versions used SIMD 2006. The change of SIMD score will produce no significant change in ASSIGN score on average as the average change is zero. Some reclassification of postcodes occurs as neighbourhoods change over time. The ASSIGN score is not primarily designed for multiple retesting of individuals already tested, so SIMD change over time should not be a problem. In persons retested after some years, change of age is likely to be more important than any change in SIMD score. Advantage of updating the SIMD score for ASSIGN is that it now covers newer postcodes previously unavailable, and also reflects changes in wealth and poverty across Scotland.
Postcodes in Scotland
The postcode is equivalent to the North American Zipcode. It defines a small population by place of residence. There are approximately a quarter of a million full postcodes in Scotland, population five million people, so on average they cover only 20 people. Each postcode can be matched with a SIMD (see above) score based on census and other social information from different agencies. Place of residence is a powerful descriptor of social status, an association long recognised and increasingly used by commerce as well as government agencies. Extreme SIMD scores are found in cities where there are extremes of wealth and therefore social stratification, so localities will differ in wealth across the city but, within each small area, the inhabitants will be similar. In rural areas, extremes of wealth are often found within one postcode so postcodes are less discriminatory
There may be occasional postcodes that are not recognised or do not have a SIMD score allocated. In such a case, try changing the final letter of the postcode until a result is obtained. In heterogeneous rural areas where the SIMD score seems inappropriate to the social status of the person being coded you should consider adjusting the SIMD or the final ASSIGN score to reflect this potential misclassification. In most cases the software will give you an estimated SIMD.
However, be sure to enter the postcode correctly, including the space between the first three and second three characters in a six-digit postcode, as this affects the interpretation.
Homelessness, prison population, inappropriate postcode etc
For severely deprived minorities, those who are homeless, travellers etc or those who would be identified by a postcode which wrongly minimizes their obvious social deprivation it is possible to enter a substitute postcode.
This is QQ1 1QQ which has an SIMD 2012 score of 48.8, placing it in the middle of the most deprived fifth of the Scottish population. It was created specifically for the ASSIGN-SCORE postcode look-up table, and should be used for that purpose only. Its use should be confidential to patient medical records and not used pejoratively. (Letters posted to QQ1 1QQ will not be delivered by the Post Office, as it does not exist in reality.)