sion of U.S. systems, we focus attention on the current revision plans for the Standard Occupational Classification. This revision promises a number of important advances over existing systems, including the provision for assimilating new occupations into the system on an ongoing basis.

International Standard Classification of Occupations

The International Standard Classification of Occupations (ISCO) has three objectives: (1) to facilitate international communication about occupations through its use internationally; (2) to provide international occupational data for research, decision making, and other activities; and (3) to serve as a model, but not a replacement, for countries developing or revising their national occupation classifications. The development of this structure was based on the recommendations and decisions of the Thirteenth and Fourteenth International Conferences of Labour Statisticians, held at the International Labour Office, Geneva, in 1982 and 1987. The underlying source data consist of population censuses, statistical surveys, and administrative records maintained at the national level. ISCO-88 is the 1988 revision of the 1968 version of the classification system (International Labour Office, 1990).

The ISCO system uses two key concepts: job and skill. Job is defined as "a set of tasks and duties executed, or meant to be executed, by one person." Skill is defined as "the ability to carry out the tasks and duties of a given job." The ISCO-88 structure is hierarchical, with 10 major groups at the top, 28 submajor groups, 116 minor groups, and 390 unit groups.

Although ISCO-88 was not intended to be the single structure that would fit all nations, many nations have adopted the ISCO system with little or no modification (Elias, 1993). Western nations have tended to make more substantial modifications to ISCO-88 or to devise their own structures (Wootton, 1993). Australia, Canada, the United Kingdom, and the Netherlands are primary examples. Table 5.2 presents comparative information about ISCO-88 and its adaptation for use in those countries. Shown are the key classification concepts, the number of levels in the hierarchical ladder, and the number of occupational groups in each level. All of the systems have fewer than a dozen broad



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