Methodological Causes of Asymmetries

The most common causes of methodological asymmetries are the following:

• simplified product reporting: Where the EU legislation allows simplified codification of goods for certain transactions, some Member States apply the simplifications but others do not;
• Only export/dispatches to be reported in the case of supplies to ships and aircraft;
• different approaches to estimating or compiling trade data for specific goods and movements not covered by customs or statistical declarations, such as gas, electricity, vessels or aircraft;
• confidentiality: It is possible that data are considered confidential by only one of the two partners. However, the application of the confidentiality procedures should not impact the results at total trade level;
• time lag: the same operation can be recorded under a different reference period because of transport times or processing delays;
• CIF/FOB valuation: imports are valued on a CIF basis and exports on a FOB basis. This causes a systematic asymmetry as the value of the imports should then be higher than the value of the mirror exports;
• differences in methods and data used to estimate missing trade;
• different practices in the treatment of revisions;
• currency conversion; and
• other methodological differences such as definition of partner country, definition of statistical territory, trade system (special or general).