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 0.54 to 87.6 (2004 version). By population fifths from 1 (least deprived) to 5 (most deprived) the categories are:
| Least Deprived | Most Deprived | ||||
| Population Fifth | First | Second | Third | Fourth | Fifth |
| SIMD Score Range (inclusive) | 0.54 to 7.63 | 7.64 to 13.49 | 13.50 to 21.16 | 21.17 to 33.93 | 33.94 to 87.60 |
The SIMD distribution therefore has a long tail and shows a positive skew. The mean value is approximately 28 and the median 20.
The SIMD was revised in 2006 and again in 2008 (for publication autumn 2009). Although there have been some changes to the score both in its derivation and in relative movements up and down in the scores of different localities, the range and mean values are very similar and there is a very high correlation between postcode SIMD scores for 2004 and 2006 and now 2008. 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 10-20 years ago were used with follow-up data collected since then, and 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 in two modes. In ASSIGN and Comparison with Framingham> mode SIMD scores are looked up by postcode.The ASSIGN score was originally calculated using the SIMD from 2004. ASSIGN score version 3.1, published in 2008 used SIMD 2006. ASSIGN score version 3.2 published in late 2009 will use SIMD 2008
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 social stratification, so localities are very diverse across the city but homogeneous within each locality. They are less discriminatory in thinly populated rural area where close neighbours may vary considerably in wealth, occupation and education.
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.