As discussed in chapter 1 an individual’s occupation is considered to be a key dimension of socioeconomic position and an important means of social stratification. All
occupational information in SHARE was recorded using the 1988 version of the
International Standard Classification of Occupations (ISCO-88) published in 1990 by the International Labour Organization (ILO) (International Labour Organization, 1990), which is now the most widely used occupational classification system (Bergman & Joye, 2005).
ISCO was developed to provide an internationally comparable classification system for
the coding of occupational information (usually job titles) into specific groups based on the tasks and duties relating to different jobs (Hoffmann & United Nations Statistics Division, 1999). The ILO define a job as a set of tasks and duties designed (by an employer) to be performed by an individual (the employee) (Elias, 1997). Previous versions of ISCO (ISCO-58 and ISCO-68) grouped occupations by their skill specialisation, which refers to the field(s) of knowledge needed, tools and machinery used, material worked on, and type of goods and services produced (Elias, 1997). In ISCO-88, jobs are classified both according to the skill specialisation and skill level. The skill level
corresponds to the degree of complexity, range of tasks, and responsibilities involved in a particular job, and is related to the amount of formal education, formal and informal training, and work experience required for the satisfactory performance of a job. Thus, the skill level required to perform a particular job does not necessarily relate to the educational qualifications or skills of an individual employed to do that job, but rather the skill level needed to perform the tasks and duties of the job (Wolf, 1997). A key
assumption of ISCO-88 is that the tasks and duties associated with a specific occupation are similar over time and across countries (Bergman & Joye, 2005).
ISCO-88 (Table 4.4) has a hierarchical structure containing four levels; each increase in level provides a greater degree of detail in the job titles (Wolf, 1997). At the least detailed level (major group) there are 10 categories differentiated by the industry of the job and the skill level needed for adequate performance of the job. Groups 1 to 5 roughly correspond to non-manual ‘white collar’ occupations and groups 6 to 10 to manual ‘blue collar’ occupations (Elias, 1997). The 10 major groups are divided into sub-major, minor, and unit groups, with 390 different categories at the unit group level. For example, elementary occupations (major group 9) contains sales and services elementary occupations (sub-major group 91), which includes street vendors and related workers (minor group 911), which contains door-to-door and telephone salespersons (unit group 9113). ISCO-88 does not differentiate between employers and employees, or between supervisors and the supervised. Thus, these groups are coded according to the type of job they perform according to its tasks and duties.
Table 4.4: ISCO-88 major groups with number of subgroups and skill levels, adapted from ILO (1990).
ISCO-88 Major Group
Sub-major
1. Legislators, senior officials and managers
- 8 33 -
2. Professionals 4 18 55 4th
3. Technicians and associate professionals
4 54 73 3rd
4. Clerk 2 7 23 2nd
5. Service workers and shop and market sales workers
2 9 23 2nd
6. Skilled agricultural and fishery workers
2 6 17 2nd
7. Craft and related workers 4 16 70 2nd
8. Plant and machine operators and assemblers
2 20 70 2nd
9. Elementary occupations 3 10 25 1st
10. Armed forces 1 1 1 -
Totals 28 116 390 -
There were some differences in the coding of occupations in SHARE during Wave 1 compared to other waves. During Wave 1, occupations were coded to the most detailed unit grouping of ISCO-88. This coding process is a lengthy and expensive task (Elias, 1997). Adding the extra detail adds a huge burden on the coding process in any survey (Ganzeboom, 2010), which is especially onerous in cross-national surveys which require translation into English. Indeed, some of the occupational information collected in Wave 2 during 2006/07 has still not been coded to a level that would be suitable for public release. Recoding occupational titles to more detailed groupings is also subject to a greater degree of measurement error and misclassification bias (Lambert et al., 2008). It has been shown that when using more detailed ‘minor group’ classifications of
occupations, agreement rates between coders of above 75% are difficult to achieve.
Rates in some studies were as low as 56% (Elias, 1997). Coder agreement using less detailed groupings (such as the major group) is higher, generally above 80%. Researchers involved in the SHARE project were aware that the detailed occupational groupings collected during Wave 1 were not being used very often (Wahrendorf, 2011) and,
therefore, the justification for collecting such detailed information was questionable.
Thus, it was not surprising that in the following survey waves (including the occupational histories collected in SHARELIFE) occupational information was only collected using the least detailed major group level.
Although there are several advantages of collecting less detailed occupational
information, operationalisation into measures of occupational position is made more difficult as a result of the loss in detail. As outlined above (Table 4.4), the ILO classifies the major groups of ISCO-88 into four quasi-hierarchical skill levels. ISCO-88 is similar to the 1980 version of the Registrar General’s Classification of Occupations for use in the United Kingdom, which is based on the skill level of occupations (Brewer, 1986). The ILO provides an indication of the educational qualifications associated with each skill level (Table 4.5), but caution that this does not have to be gained via formal education qualifications, as mentioned above.
Table 4.5: ISCO-88 skill levels and education/qualifications (adapted from ILO, 1990).
Skill Level Corresponding Education /Qualifications
1 Primary education (begun at ages 5-7 and lasting approximately 5 years) 2 Secondary education (begun at ages 11-12 and lasting 5-7 years)
3 Tertiary education (begun at ages 17-18 and lasting 3-4 years, but not giving equivalent of University degree)
4 Tertiary education (begun at ages 17-18 and lasting 3-6 years and leading to University degree or equivalent)
The lowest skill level (1) includes elementary occupations, such as domestic cleaners or building caretakers, whereas the highest skill level (4) includes professional occupations, such as medical or teaching professionals. No specific skill level is provided by the ILO for the major groups 1 and 10, which correspond to legislators, senior officials, and
managers, and the armed forces respectively. This was because the ILO considered the variety of tasks that comprise managerial and armed forces roles too diverse to
correspond to a specific skill level, and the information needed to classify armed forces occupations, in particular, is often not provided (Elias, 1997). For the purpose of this thesis, and to prevent discarding individuals in these groups, legislators, senior officials,
and managers were assigned to the highest skill level (4), joining the professional
occupations. This decision was based on the premise that the occupational skill level can be considered as an indicator of socioeconomic status. Legislators, senior officials, and managers are considered to be occupations of high prestige (Ganzeboom & Treiman, 1996), therefore categorising them in the same group as professional occupations is considered appropriate.
The armed forces occupational group is less straightforward. There is no good theoretical reason to exclude this group, although within public health research it has often been standard practice to do this (Galobardes et al., 2006b). Discarding individuals who reported any length of armed forces service during the recall of their occupational histories would result in the loss of 464 individuals. An additional 288 individuals who reported the main breadwinner when they were 10 years old was in the armed forces would also have to be dropped. However, as there is no information on the role or rank of the individual in the armed forces it is not entirely clear how this group should be treated. A similar approach to Walker (2010) was taken to classify this group. In his thesis, which examined environmental influences over the life course and
cardio-respiratory health, he argued that armed forces occupations were most likely to resemble manual, lower status occupations, characterised by low job control and exposure to hazardous occupational exposures. Armed force service was therefore considered to be a disadvantaged state, equivalent to a manual occupation. In terms of the skill level,
Ganzeboom and Treiman (1996) treat ordinary soldiers as belonging to the ISCO-88 major group 5 (service workers and shop and market sales workers), which corresponds to the second skill level. Therefore, this approach was taken in this study.
In addition to deriving the skill level of the occupation from ISCO-88 codes, several other classification systems have been produced to provide internationally comparable and theoretically informed measures of occupational position, including the Erikson and Goldthorpe social class scheme (EGP), the International Socio-Economic Index of Occupational Status (ISEI), and the Standard International Occupational Prestige Scale (SIOPS) (Ganzeboom & Treiman, 1996). The EGP class scheme aims to “differentiate positions within labour markets and productions units or, more specifically, one could say, to differentiate such positions in terms of the employment relations that they entail”
(Erikson & Goldthorpe, 1992. p37, emphasis in original). Thus, they view employment
relations to be the key to class divisions and differentiate between employers (who purchase labour and exert control and authority over workers), self-employed workers without employees (who do not purchase or sell their own labour), and employees (who sell their own labour and are somewhat controlled by employers) (Erikson & Goldthorpe, 1992). Several versions of the EGP class scheme have been developed and it can be operationalised from ISCO-88 codes with additional information relating to the
individual’s employment and supervisory status (Ganzeboom & Treiman, 1996). As will be discussed in the methodology, it was important to have hierarchical measures of socioeconomic position. The EGP scheme does not have an inherent hierarchical rank (Galobardes et al., 2006b) and unfortunately supervisory status was not collected in the job history interviews. Therefore this scheme was not considered further in this thesis.
Two measures of socioeconomic status can be derived from ISCO-88 codes: the International Socio-Economic Index of Occupational Status (ISEI) and the Standard
International Occupational Prestige Scale (SIOPS). These two measures differ from EGP in that they are intended to be continuous scales rather than class categories. ISEI is a socioeconomic status scale which seeks to measure “the attributes of occupations that convert a person’s main resource (education) into a person’s main reward (income)”
(Ganzeboom et al., 1992. p9). Its theoretical basis and interpretation is less well
established, although it is highly correlated with SIOPS. ISEI is perhaps more similar to the skill level of occupations compared to SIOPS, thus the latter is used in this thesis.
Occupational prestige refers to the “metric of ‘moral worth,’ and the moral worth of positions reflects their control over socially valued resources and rewards, that is, their power and privilege” (Treiman, 1976. p289). Thus, high prestige is associated with occupations that hold most power (control over limited and desirable resources, such as knowledge, skills, or economic resources) which creates disparities in privilege (Bergman
& Joye, 2005). Although there had been previous studies which assessed the subjective prestige of occupations, in his seminal work, Treiman developed a Theory of Occupational Prestige after analysing the prestige of occupations in 60 countries (Treiman, 1977).
Treiman argued that the prestige rating of an occupation places an individual within the social structure and provides an indication of the individual’s attitudes, experiences, and life style (Bergman & Joye, 2005; Treiman, 1977). His analysis demonstrated the general consistency of subjective prestige ratings of occupations between societies and over time.
His work resulted in the generation of a universal standard prestige scale which could be used worldwide. Ganzeboom and Treiman (1996) have since updated this scale to be used with the ISCO-88 classification of occupations (Treiman’s 1977 analysis used ISCO-68 codes) and provided prestige ratings for each ISCO-88 occupation. Ideally SIOPS would be operationalised from the most detailed ISCO-88 codes. However, as discussed above, these were not available for most of the occupational information in SHARE. Ganzeboom and Treiman (1996) provide prestige ratings for each ISCO-88 level including the 10 major groups used in this study (Table 4.6). These were calculated from the “weighted average of the scores for the lower-level titles contained in the category, where the weights are proportional to the number of men in each category” (Ganzeboom & Treiman, 1996.
p211). As for the skill level classification, members of the armed forces were treated as service workers. The prestige rank for this group was 32, which also approximates the mean of the SIOPS rankings for the other manual occupations (ISCO-88 groups 6 to 9).
Table 4.6: Major ISCO-88 groups and the corresponding SIOPS ranking
Major ISCO-88 Group SIOPS ranking
1. Legislators, senior officials and managers 51
2. Professionals 62
3. Technicians and associate professionals 48
4. Clerk 37
5. Service workers and shop and market sales workers 32
6. Skilled agricultural and fishery workers 37
7. Craft and related workers 38
8. Plant and machine operators and assemblers 34
9. Elementary occupations 21
10. Armed forces 32
To summarise, occupational information in SHARE was recoded using the major groups of ISCO-88. These were operationalised into three measures: manual versus non-manual, skill level, and occupational prestige (SIOPS). Two other issues arose in the classification of occupations and these are discussed in section 4.4.3: the classification of women and
the treatment of periods out of the labour force. First, the specific measures of childhood and adulthood socioeconomic position used in this study are described below.