It is difficult to gauge the effect of tariff barriers among countries. Clearly, the way in which import demand responds to changes in tariffs will depend on a variety of factors. These include the reaction of producers and consumers to price changes, the share of imports in domestic production and consumption, the substitutability of imports for domestic products, and so on. The reaction to tariff levels will differ from country to country as well as from commodity to commodity. Thus, the amount of a tariff does not necessarily determine its restrictive effect. Typically, such comparisons apply only to products for which tariffs are the major protective device. This is generally true for nonagricultural products in developed countries (other strategies, such as import quotas, are a common means of protecting agricultural commodities). Although tariffs on imported raw materials will protect domestic producers of those commodities, such tariffs will also increase the costs to domestic manufacturers who use those raw materials. These conditions necessitate a distinction between nominal and effective rates of protection.

The nominal rate of protection is the percentage tariff imposed on a product as it enters the country. For example, if a tariff of 20 percent of value is collected on clothing as it enters the country, then the nominal rate of protection is that same 20 percent.

The effective rate of protection is a more complex concept: consider that the same product—clothing—costs $100 on international markets. The material that is imported to make the clothing (material inputs) sells for $60. In a free-trade situation, a firm can charge no more than $100 for a similar piece of clothing (ignoring transportation costs). Importing the fabric for $60, the clothing manufacturer can add a maximum of $40 for labour, profit markup, rents, and the like. This $40 difference between the $60 cost of material inputs and the price of the product is called the value added.

The same situation may be considered with tariffs—say, 20 percent on clothing and 10 percent on fabric. The 20 percent tariff on clothing would raise the domestic price by $20 to $120, while a 10 percent tariff on fabrics would increase material costs to the domestic producer by $6 to $66. Protection would thus enable the firm to operate with a value-added margin of $54—the difference between the domestic price of $120 and the material cost of $66. The difference between the value added of $40 without tariff protection and that of $54 with it provides a margin of $14. This means that the effective rate of protection of the domestic processing activity—the ratio of $14 to $40—would be 35 percent. The effective rate of protection derived—35 percent—is greater than the nominal rate of only 20 percent. This will be the case whenever the tariff rate on the final product is greater than the tariff on inputs. Because countries generally do levy higher tariffs on final products than on inputs, effective rates of protection are usually higher than nominal rates—often much higher.

The effective rate of protection also depends on the share of value added in the product price. Effective rates can be very high if value added to the imported commodity is a small percentage or very low if value added is a large percentage of the total price. Thus, effective protection in one country may be much higher than that in another even though its nominal tariffs are lower, if it tends to import commodities of a high level of fabrication with correspondingly low ratios of value added to product price.

Other government regulations and practices may also act as barriers to trade. Quotas or quantitative restrictions may prohibit the importation of certain commodities or limit the amounts imported. Such quotas are usually administered by requiring importers to have licenses to import particular products. Quotas raise prices just as tariffs do, but, being set in physical terms, their impact on imports is direct, with an absolute ceiling set on quantity. Increased prices will not bring more goods in. There is also a difference between tariffs and quotas in their effect on revenues. With tariffs, the government receives the revenue: under quotas, the import license holders obtain a windfall in the form of the difference between the high domestic price and the low international price of the import.

Another barrier is the voluntary export restraint (VER), noted for having a less-damaging effect on the political relations between countries. It is also relatively easy to remove. This approach was applied in the early 1980s when Japanese automakers, under pressure from U.S. competitors, “voluntarily” limited their exports of automobiles to the U.S. market. Like quotas, VERs limit the quantity of trade and therefore tend to raise the prices of imported goods. In this case, the VER made Japanese automobiles less available in the United States and raised the prices that U.S. consumers had to pay for them, thereby making domestically produced cars more attractive. This approach also allowed Japanese exporters to charge higher prices. As a result, the Japanese exporters, rather than U.S. importers, reaped much of the windfall from the VER. VERs are usually not voluntary in any meaningful sense. In this example, the Japanese automakers agreed to a VER in order to avoid a U.S. import quota.

Still other barriers include state trading organizations and government procurement practices that may be used preferentially. In the United States, “buy American” legislation requires government procurement agencies to favour domestic goods. Customs classification and valuation procedures, health regulations, and marking requirements may also have a restrictive effect on trade. Japan, for example, has restricted imports of U.S. apples on the grounds that the apples could be contaminated with the fire blight disease. Finally, excise taxes may act as a barrier to trade if they are levied at higher rates on imports than on domestic goods.

Much of the industrialization that took place in the late 20th century in some less-developed countries was characterized by the expansion of import-competing industries protected by high tariff walls. In many of those countries, tariffs and various quantitative restrictions on manufactured goods were high, but the effective rates of protection were often even higher, because the goods tended to be highly fabricated and the proportion of value added in production after importation was low. While countries such as Taiwan, Hong Kong, and South Korea oriented their manufacturing industries mainly toward export trade, they tended to be exceptional cases. More commonly, developing nations have mistakenly sought to compete with foreign-made goods for the domestic market. High protection in these countries has often contributed to a slowdown in production, while the export of primary commodities has discouraged expansion of exports of the more valuable manufactured goods. Although domestic production of nondurable consumer goods fosters rapid economic growth at an early stage, less-developed countries have encountered considerable difficulties in producing more-sophisticated, value-added commodities. They suffer all the disadvantages of small domestic markets, in addition to a lack of incentives for technological improvement.