In many developing countries, total tax revenue is derived from three main sources: domestic taxes on goods and services (sales and excise taxes), direct taxes (primarily on corporations), and, most important, taxes on foreign trade (import duties). But, as trade liberalization has lowered tariffs and duties, the share of trade taxes has declined, while other sources have not compensated for falling trade revenue.
在许多发展中国家，税收总收入有三个主要来源：对商品和服务收取的国内税（销售税和消费税）、直接税（主要对公司收取）以及最重要的对外贸易税（进口关税）。但是，随着贸易自由化降低了关税，贸易税的比重有所降低，而其他收入源又不足以补偿贸易税收入的下降。