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15.41. Consistent with other economic statistics, activity should be recorded as it occurs rather than when the related payment is made (accrual basis). Flow variables should be recorded for the whole reference period, while stock variables should, if possible, be recorded from the end of the reference period. An exception is the employment variable, for which use of a period average is preferable (see also section D.4) if the employment is subject to strong seasonal variation. Data for a given reference period are mainly valued at the average prices and, if relevant, average exchange rates of that period. For stock variables (for example, property plant and equipment), values of source data might be recorded at historical cost and will largely reflect prices at the time the asset was acquired rather than the prices of the reference period. In such a case, revaluations to reflect current-period prices should be made by the compiler.
Next: D.3. Treating the activities of special purpose entities in a FATS context
[1] Measuring Globalization: OECD Handbook on Economic Globalization Indicators (HEGI) recommends that the calendar year be used as a reference period.