Scottish Longitudinal Study
Development & Support Unit

Completed Projects

Project Title:

Understanding changes in NS-SEC between census and death

Project Number:



Alastair Leyland (Medical Research Council)
Ruth Dundas (Medical Research Council)

Start Date:

Approved on 22-01-2008


The mismatch between NS-SEC recorded on death records (numerator) and the Census population (denominator) makes it impossible to examine the gradient in mortality across individual socio-economic circumstances with any confidence. At its simplest the problem relates to the proportion of each group (numerator and denominator) that have NS-SEC assigned. At younger ages both groups receive poor coverage in the Census: 47% of men aged 16-19 and 76% aged 20-24 in Scotland were assigned an NS-SEC in the 2001 Census. The problem is also acute at older ages with 73% of men aged 60-64 and 13% aged 65-69 having an NS-SEC. For death records the coverage is poor at lower ages (49% and 68% of men aged 16-19 and 20-24 had NS-SEC allocated on death records 2000-02) but high amongst the older population (97% of male deaths at ages 60-69). There are also considerable discrepancies at ages between these extremes; by way of example, only 4% of the Census population but 22% of the deaths among men aged 30-34 were not classified.[1]

The proportions allocated NS-SEC from both sources are lower among women than among men. For women, however, disparities between the use of categories are also clear. For example, the mortality rate for women in “higher managerial and professional occupations” at ages 20-59 was 358 per 100,000 – compared with a rate of 170 per 100,000 among men of the same ages – whilst the rate among semi-routine occupations for women at these ages was just 166 per 100,000 (567 for men).[2] The fact that the gradient for men goes in the expected direction does not mean that the classification to NS-SEC is the same for numerator and denominator. Systematic biases due to coding have been found in England, but even after adjustment population mortality rates differed from those seen in the LS.[3]

Finally, regional differences in mortality in NS-SEC groups should be understood better to ensure that these do not reflect coding differences. For example, the mortality rate among “small employees and own account workers” among men 20-59 in Aberdeen was 303 per 100,000 compared to a Scottish average of 188.

The study aims to improve our understanding of the mismatch between NS-SEC codes given on death records in 2000-02 and the NS-SEC codes for the general population that can be obtained from the 2001 Census in Scotland. More precisely, it will develop probabilities of transition from NS-SEC code given at the time of the Census to NS-SEC code at time of death taking into account as many of age, sex, year and cause of death, area of residence and marital status as is practical. We will also calculate mortality rates for the SLS sample to compare with the population (by age, sex, NS-SEC etc).


  1. Leyland AH, Dundas R, McLoone P, Boddy FA. Inequalities in mortality in Scotland 1981-2001. MRC Social and Public Health Sciences Unit Occasional Paper no. 16. Glasgow, MRC Social and Public Health Sciences Unit, 2007.

  2. Appendix available from

  3. White C, Glickman M, Johnson B, Corbin T. Social inequalities in adult male mortality by the National Statistics Socio-Economic Classification, England and Wales, 2001-03.

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