Aggregation of Data
Different units of measurement are collected for different commodities within the classification nomenclature. Quantity should be consistent up to 2-digit level at which point there may be differences (e.g. one Chapter of the nomenclature may require litres, another kilograms etc.). The nature of supplementary units can also be different at a much more detailed level (e.g. the requirement for one 8-digit commodity code could be square metres, another could be cubic metres).
Care should be taken when analysing aggregated data presented, particularly by users building data within the interactive data tables. In particular, when aggregating above 8-digit level the figure created for supplementary units may be unreliable. This may also be the case for the figure created for quantity above 2-digit level. However, value (GB Pounds Sterling) is consistent throughout and can be reliably aggregated.
Additionally, from January 2006 Intrastat regulations only require the declaration of either a net mass or a supplementary unit value per line of trade, to reduce the administrative burden on the data provider. This means that for certain commodity codes the submission of a quantity (net mass) value is not required for EU trade declarations. Consequently, the quantity (net mass) data published within the OTS for those commodity codes may not reflect the actual quantity (net mass) of traded goods.
From January 2010 an estimate of the quantity (net mass) will be published for those commodity codes where net mass is optional and it has not been collected from the EU trade declaration. Further information is available in the 'Methodology & Policies' area of 'About OTS'. For periods between January 2006 and December 2009, use of the reported quantity (net mass) totals for the commodity codes affected is not recommended. This also applies to higher aggregates of the data e.g. 4-digit data and SITC totals.
Non-EU trade totals for quantity are unaffected by the Intrastat regulation and estimation procedures. Consequently using aggregate quantity data for combined EU and non-EU trade is not recommended.