Book excerpt: The International Standard Classification of Occupations 2008 (ISCO-08) is a four-level hierarchically structured classification that covers all jobs in the world. Developed with the benefit of accumulated national and international experience as well as the help of experts from many countries and agencies, ISCO-08 is fully supported by the international community as an accepted standard for international labour statistics. ISCO-08 classifies jobs into 436 unit groups. These unit groups are aggregated into 130 minor groups, 43 sub-major groups and 10 major groups, based on their similarity in terms of the skill level and skill specialisation required for the jobs. This allows the production of relatively detailed internationally comparable data as well as summary information for only 10 groups at the highest level of aggregation. Each group in the classification is designated by a title and code number and is associated with a definition that specifies the scope of the group. The classification is divided into two volumes: Volume I presents the structure and definitions of all groups in ISCO-08 and their correspondence with ISCO-88, which it supersedes, while Volume II provides an updated and expanded index of occupational titles and associated ISCO-08 and ISCO-88 codes.