International Standard Classification of Occupations
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International Labour Organization standard for job names
The International Standard Classification of Occupations (ISCO) is a system developed by the International Labour Organization (ILO) to classify and organize occupations into a structured hierarchy. It serves to facilitate international communication about occupations by providing a framework for statisticians to make internationally comparable occupational data available.
seek[ing] to facilitate international communication about occupations by providing statisticians with a framework to make internationally comparable occupational data available, and by allowing international occupational data to be produced in a form that can be useful for research as well as for specific decision-making and action-oriented activities.
According to the ILO, a job is defined as "a set of tasks and duties performed, or meant to be performed, by one person, including for an employer or in self-employment." Occupation refers to the kind of work performed in a job, and the concept of occupation is defined as "a set of jobs whose main tasks and duties are characterized by a high degree of similarity." A person may be associated with an occupation through the main job currently held, a second job, a future job, or a job previously held. Skill, in this context, is the ability to carry out the tasks and duties of a job.[2]
The latest version, ISCO-08, was adopted in 2008 and includes four classification levels: major groups, sub-major groups, minor groups, and unit groups. It is widely used for comparative labor market studies, policy development, and international reporting, including within the European Union, the United Nations, and other global institutions.
History
The origins of ISCO trace back to the mid-20th century when the need for a global occupational classification system became evident at the First International Conference of Labour Statisticians (ICLS) in 1923.[3] The first complete version, ISCO-58, was adopted in 1957 by the Ninth ICLS and published in 1958, providing a systematic method for grouping occupations to support labor market analysis and facilitate international comparisons. Subsequent revisions, including ISCO-68, ISCO-88, and ISCO-08, refined the classification criteria to reflect changing labor market structures, technological advancements, and evolving job roles. ISCO has since been widely adopted by national governments and international organizations to align workforce data with global labor market trends. The continuous adaptation of ISCO reflects the necessity of ensuring its relevance amid shifts in employment patterns, technological progress, and the emergence of new economic sectors. Moreover, its role in international labor statistics enables cross-country comparisons, aiding in policy formulation and economic planning.[4][5]
The ISCO-08 revision was developed through consultations with national governments, labor organizations, and international experts to ensure relevance and adaptability. Looking ahead, future iterations of ISCO are expected to incorporate new occupational categories reflecting automation, digital transformation, and emerging industries. The adaptation of ISCO-08 for national use is a critical process to ensure its applicability across diverse labor markets. Countries often modify ISCO-08 to align with national occupational classifications while maintaining international comparability. For instance, the European Union, through the European Skills, Competences, Qualifications and Occupations (ESCO) framework, has built upon ISCO-08 by incorporating more detailed competencies and qualifications for cross-border labor mobility.[6] This adaptation process involves mapping national job structures to ISCO categories, refining classifications to reflect local labor market conditions, and ensuring consistency in data reporting for global labor statistics.[5] Of note, Donald Treiman developed the Standard International Occupational Prestige Scale using the ISCO.[7]
The ISCO-08 structure
ISCO-08 organizes occupations into a four-level hierarchical system:
Major Groups (10 broad occupational categories)
Sub-Major Groups (43 broader occupational categories within the major groups)
Minor Groups (130 more specific job groupings)
Unit Groups (436 detailed occupational categories)
The methodology for collecting occupation data involves structured survey questions that aim to capture essential details about a person's employment. Typical questions include:
Occupation or job title: Respondents are asked to provide their official title.
Tasks and duties: A detailed description of the primary tasks performed in the role.
Work context: Information about whether the work is performed for an employer, is self-employed, or involves the production of goods for sale or personal use.
To maintain accuracy, ISCO coding is subject to quality control measures such as:
Cross-validation: Comparing coded occupations with industry classifications and job descriptions to minimize errors.
Sampling considerations: Ensuring that detailed occupational categories are statistically representative and meet publishing standards.
Error minimization: Adjustments are made to account for misclassification and ambiguous responses.
The ISCO framework is periodically reviewed and updated to reflect labor market changes, technological advancements, and shifts in workforce dynamics.
ISCO-08 skill model
ISCO-08 classifies skills into two key dimensions:
Skill level – The complexity and range of tasks required to perform an occupation, usually linked to educational qualifications or vocational training.
Skill specialization – The field of knowledge required, the necessary tools and machinery used, and the specific nature of the work performed.
Skill Level 1: Corresponds to primary education (ISCED-97 Level 1) and lower secondary education (ISCED-97 Level 2).
Skill Level 2: Corresponds to upper secondary education (ISCED-97 Level 3) and post-secondary non-tertiary education (ISCED-97 Level 4).
Skill Level 3: Corresponds to the first stage of tertiary education (ISCED-97 Level 5B), which includes vocational education and training.
Skill Level 4: Corresponds to the first and second stages of tertiary education (ISCED-97 Levels 5A and 6), which includes university degrees and advanced research qualifications.
Skill level is typically assigned at the ISCO Major Group level, except for Major Group 1: Managers and Major Group 0: Armed Forces Occupations, where it is primarily applied at the second hierarchical level (Sub Major Group level). Within each major group, organizing occupations into sub-major, minor, and unit groups is mainly based on skill specialization.[2]
Comparison with other classification systems
ISCO is one of several major occupational classification systems used worldwide. Other prominent systems include the U.S. Standard Occupational Classification (SOC), the European Skills, Competences, Qualifications and Occupations (ESCO), and national classification systems used in various countries.
U.S. Standard Occupational Classification (SOC): Developed by the U.S. Bureau of Labor Statistics, the SOC system categorizes occupations based on work performed and required skills. Unlike ISCO, which is designed for international comparisons, SOC is tailored for national employment analysis and policy-making in the U.S.[9]
European Skills, Competences, Qualifications and Occupations (ESCO): Managed by the European Commission, ESCO provides a more detailed classification system incorporating skills and qualifications. ESCO is linked to ISCO but includes a greater focus on skills mapping, making it particularly useful for workforce development and mobility within the EU.[10]
National Occupational Classification (NOC): Used in Canada, NOC aligns with ISCO but reflects country-specific labor market trends, industry demands, and workforce regulations.[11]
Occupational Information Network (O*NET): O*NET is a U.S.-specific system developed by the Department of Labor, offering detailed information on a wide range of occupations, including skills, knowledge, and abilities.[12] The Institute for Structural Research created a "crosswalk" from O*NET to ISCO-88 and ISCO-08 coding (O*NET has official crosswalks to SOC and ESCO).[13][14] Regarding skill models, both systems aim to capture the skills required for various occupations. However, O*NET provides a much more granular and comprehensive analysis of skills, including detailed ratings of their importance and level, while ISCO-08 focuses more on broader occupational categories.
Criticisms and limitations
ISCO is widely used for categorizing jobs across different sectors and countries. However, it has been subject to various criticisms and limitations. One major criticism is the challenge of cross-national comparability. Studies indicate that occupational titles coded under ISCO-08 often vary significantly between countries, raising concerns about the consistency and reliability of classifications. A study found that only 64% of job titles retained the same ISCO-08 4-digit code across multiple countries, highlighting inconsistencies in occupational classification.[15]
Evolving occupational characteristics have also posed challenges to ISCO, which relies on task similarity, duties, and required skills. Factors such as working conditions (including hours, schedules, and remote work) and the work environment (encompassing safety, health considerations, and workplace interpersonal networks) significantly influence occupational categorization.[16][17][18]
Moreover, the ISCO framework, which consists of at least ten major occupational groups, is often difficult to apply in small-scale workforce studies or in reporting partial workforce data. As a result, professionals frequently use modified classification systems tailored to specific contexts, such as distinctions between manual and non-manual labor, white- and blue-collar jobs, office-based and outdoor work, or knowledge-based and physical labor.[19][20][21][22]
The ISCO has been criticized for its broad categorization, which can group together jobs with significant differences in tasks, skills, and working conditions. For instance, the ISCO-88 version was noted to have excessive detail in some areas, such as plant and machinery operators, while providing inadequate detail in others, like service-related occupations and those prevalent in the informal sector. Additionally, there was a wide variation in the size of some sub-major and minor groups.[5]
1 2 3 4 5 6 International Labour Office, ed. (2012). Structure, group definitions and correspondence tables. International standard classification of occupations. Geneva: International Labour Office. ISBN978-92-2-125952-7.
↑ Treiman, Donald J. (1977). Occupational prestige in comparative perspective. Quantitative studies in social relations. New York: Academic Press. ISBN978-0-12-698750-8.
↑ International Labour Organization. Resolution Concerning Updating the International Standard Classification of Occupations. Adopted at the Tripartite Meeting of Experts on Labour Statistics, 6 December 2007.
↑ "SOC home". Bureau of Labor Statistics. Retrieved 13 February 2025.
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