The concepts and definitions are based on the 1998 EU Regu1ation on Short Term Statistics. National activity classification compatible to NACE rev. Monthly data are usually reported within 35 days after the reference period, and quarterly data within 90 days.
Aggregation is done as a weighted arithmetic average of quantity relatives.
Quarterly data are divided over the months on the basis of monthly turnover. When a unit refuses to respond, its data are estimated. It should be noted that the units are legally obliged to respond. Implicit in deflation process. However, the other methods do not explicitly adjust for quality differences.