Developments in sectoral and occupational classifications have a serious impact on the consistency of time series data, which are essential for comparisons of future and past trends and good forecasting. This publication highlights technical difficulties caused by changes in international classifications of sectors (NACE) and occupations (ISCO) and how these changes were managed in Cedefop’s skill forecasts results. It also explains why the transition from ISCO 88 to ISCO 08 proved more difficult than the changes from NACE rev 1.1 to NACE rev. 2.
For Cedefop’s skill and supply forecasts, despite problems with current data, there is no real alternative but to use the old system of occupational classification (ISCO 88) for the analysis and projections even though the two classifications differ substantially. To use the new ISCO 08 classification requires assuming, probably incorrectly, that occupational structures will remain unchanged in the coming years and not reflect past trends. Also, data for the new classification, for the first year or two, may not be wholly reliable. Changes may be more due to statistical factors than genuine shifts in occupational structures. However, the results using ISCO 88 are regrouped as closely as possible to the new ISCO 08. Limitations of this approach are discussed and how they may be addressed in future forecasts.