Technological characteristics are insufficient to distinguish services from goods and the classification depends sometimes upon the stage of production. Most empirical classification approaches are based on the current framework of economic analysis with its national accounting, household budgets and balance of payments, and attempt to classify service activities according to their principal functions. Despite the large shares of service output and employment in the overall economy the perception of services is still inadequate; this is a serious handicap in understanding the ongoing changes in contemporary economies. The existing international and European classification schemes are production-orientated classifications of activities used for presenting data by sector in the national accounts. The perception of the service sector is further impaired by the fact that national accounting and official employment statistics are focused on the formal economy and the institutionalized services. The measurement of services should be improved, although the difficulties of standardization make these efforts most cumbersome.