The HS is used by more than 200 countries and economies as the basis of their national tariff and statistical nomenclatures. Over 98 % of the merchandise in international trade is classified in terms of the HS. It comprises about 5,000 commodity groups; each identified by a six digit code, arranged in a legal and logical structure and is supported by well-defined rules to achieve uniform classification. It entered into force on 1 January 1988. The Harmonized System is also periodically updated and it is now the 6th edition, the 2017 version that is implemented.