Both specific and ad valorem duties are levied; but, as a member of the World Trade Organization, Angola is reviewing the need for reductions in tariffs and non-tariff barriers. Specific duties are assessed by weight. Additional taxes are levied on luxury items and preferential treatment is accorded to goods from Portugal, Mozambique, Guinea-Bissau, Cape Verde, and São Tomé and Princípe. All imports require a license and are handled by one of several state companies. Most exports are similarly handled by state agencies.