In general, data comply with the UN recommandations defined in International Merchandise Trade Statistics: Concepts and Definitions, Revision 2 (IMTS, Rev.2). For exceptions and for definitions of statistical territories, please refer to country notes. Following the UN recommendations, the international merchandise trade statistics record all goods which add to or subtract from the stock of material resources of a country by entering (imports) or leaving (exports) its economic territory. Goods simply being transported through a country (goods in transit) or temporarily admitted or withdrawn (except for goods for inward or outward processing) do not add to or subtract from the stock of material resources of a country and are not included in the international merchandise trade statistics. Customs records should be the main source of the data; and the additional sources could be used where customs sources are not available. Goods should be included in statistics at the time when they enter or leave the economic territory of a country. In the case of customs-based data collection systems, the time of recording should be the date of lodgement of the customs declaration. Lists of goods to be included, to be recorded separately and to be excluded should be provided. Specific goods are to be excluded from detailed international merchandise trade statistics but recorded separately in order to derive totals of international merchandise trade for national accounts and balance of payments purposes. Trade system There are two trade systems in common use by which international merchandise trade statistics are compiled: general trade system and special trade system. The United Nations recommendations advise using the general trade system that provides a more comprehensive recording of external trade flows than does the special system. It also provides a better approximation of the change of ownership criterion used in the 1993 SNA and BPM5. General trade includes all goods that cross the national frontier including goods that are imported into and exported from custom-bonded warehouses and free zones. The general trade system is in use when the statistical territory of a country coincides with its economic territory so that imports include all goods entering the economic territory of a compiling country and exports include all goods leaving the economic territory of a compiling country. Special trade covers goods that cross the customs frontier plus goods that are imported into and exported from custom-bonded areas. The special trade system is in use when the statistical territory comprises only a particular part of the economic territory.