As a result of post-war agreements, NTMs are now considered the most important barriers to trade (replacing tariff barriers). Their list is very long, ranging from very strict explicit (commonly called "hard-core) measures like quantitative limitations (import or export quotas) and variable levies, to rather subtle, less conspicuous measures which include: discriminatory state trading, national procurement practices, content regulations, anti-dumping legislation, marketing obstacles, packaging and labelling restrictions, safety and health requirements, customs procedures, surcharges and miscellaneous fees.
In general, the explicit measures can be expected to be the more protective than the implicit or more subtle measures. However, in some cases the explicit measures have rather modest effects on trade while more subtle measures are extremely protective. For example, an import quota is very explicit; it limits imports to a predetermined volume. To the extent that the quota limit is below the free trade volume, the quota is protective -- the lower the quota limit, the more protective the measure. However, if a quota limit is near the free trade volume, the quota would have minimal restrictive effects on trade. In contrast, a health regulation might require imported products to meet certain standards that are equivalent to those required of domestic goods. So long as the foreign producer is able to comply with those standards, the measure would have no protective effect at all. On the other hand, if the foreign producer cannot meet the standard, imports would be prohibited; the protective effect is the most extreme possible. In this way, tariff concessions may be rendered partly or wholly ineffective by non-tariff restrictions.
Quantifying the effects of non-tariff measures on international trade flows is most difficult. One must first identify the non-tariff measure facing exporting countries. Second, the identified measures must be categorized to determine which measures are likely to have the more adverse effect on exports. And finally, the costs to the exporting countries of these measures must be estimated.
Aside from this general area, the major product sectors in which developing countries were subject to an explicit non-tariff measure were seafood in Japan; sugar in the EEC/EU, Japan and the USA; tuna and steel products in the USA; and agricultural products, consumer electronics, footwear and steel products in the EC. Excluding MFA-restrained products, total exports valued at $25.6 billion were affected. This means that an above-average proportion of imports from developing countries into the developed market economies is subject to non-tariff barriers. It has been estimated that 28% of the value of imports from developing countries is subject to these restrictions, as compared with 11% for imports from the rest of the world. In total, non-tariff measures lowered exports from developing countries by an estimated $4.6 billion, or by 18% of their current exports of the products to the restraining countries.
NTM-affected imports in 10 select OECD "countries", including the EEC/EU (millions of USA dollars) in 1986 were Austria (8.7), EEC/EU (4,216.3), USA (1,635.8), Canada (934.8), Japan (439.4), Norway (134.6), Switzerland (88.0), Sweden (50.6), Finland (47.3), a total of $7,655.5 million.