10.24 The establishment of a comprehensive system of price and volume indices covering all supply and uses of goods and services encounters a particular difficulty when measuring the output of non-market services. These services differ from market services in that they are not sold at a market price and their value at current prices is calculated by convention as the sum of the costs incurred. These costs are intermediate consumption, compensation of employees, other taxes less subsidies on production and consumption of fixed capital.
10.25 In the absence of a unit market price, the change in the 'unit cost' of a non-market service can be considered as an approximation of the change in the price. If non-market services are consumed on an individual basis, it is in principle possible to estimate quantities which are homogeneous and which reflect the utilisation of these services and apply the unit costs of a base year to obtain data in constant prices. By such type of output-measurement it will be possible to analyse changes in productivity for individual non-market services. For collective services it is generally not possible to establish unit costs and quantities reflecting their utilisation. If attempts are made to account for changes in productivity for collective services by indirect methods, users should be made aware of this.
10.26 In the context of the economic accounts, it is of prime importance to adopt the principle that the production and consumption of non-market services, like the production and consumption of goods and market services, must be defined in terms of the actual flows of these goods and services and not in terms of final results obtained from their use. As these results depend on several other factors as well, it is not possible to measure, for example, the volume of teaching services by the rise in the level of education, or the volume of health services by the improvement in the health of the population.