Most nations are now members of the multilateral trade agreements of the World Trade Organization. Free trade was best illustrated by Britain`s unilateral attitude, which reduced rules and tariffs on imports and exports from the mid-19th century to the 1920s.  An alternative approach of creating free trade zones between groups of countries of mutual agreement, such as those in the European Economic Area and the open markets of Mercosur, creates a protectionist barrier between this free trade area and the rest of the world. Most governments continue to follow certain protectionist measures to promote local employment, such as tariffs on imports or export subsidies. Governments can also restrict free trade in order to limit exports of natural resources. Other barriers to trade are import quotas, taxes and non-tariff barriers, such as legislation.B. A number of factors can influence the terms of trade, including changes in derintis or supply or government policy. In a succinct example, the terms of trade, when Japanese demand for aircraft increases, will move in favor of the United States, as they may require more televisions for each aircraft. When the Japanese start producing aircraft, the terms of trade will change in Japan`s favour, as the supply of aircraft will now be greater and the Japanese will have other sources of supply.
Access to other markets plays an important role in this business model, where comparative advantages can be created. In the absence of free trade, it is extremely costly for a government to subsidize a new entrant, as the subsidy must be relaxed, both to overcome the barriers of foreign trade and to stimulate the domestic producer. The WTO-U.S. free trade agreements also play an important role in establishing rules governing what a country can do in many areas to create comparative advantages; For example, the grant code limits the nature of the subsidies that governments can provide. In addition, some products do not use the same production factors over their life cycle.  For example, when computers were first introduced, they were incredibly capital-intensive and needed a highly skilled workforce. Over time, as the volume increased, costs decreased and computers were mass-produced. In the beginning, the United States had a comparative advantage in production; but today, while computers are mass-produced by relatively unskilled labour, the comparative advantage has shifted to countries where labour is plentiful and cheap. And other products can use different production factors in different countries. For example, cotton production is very mechanized in the United States, but it is very laborious in Africa. The fact that the factors of production may change does not negate the comparative advantage theory; it simply means that the package of products that a nation can produce relatively effectively can change only its trading partners. One theory designed to explain why different countries specialize in different goods is the Heckscher-Ohlin theory.
This theory says that countries will tend to export products that need more inputs from a production factor (capital, land, labour) than they have in abundance, and vice versa, to import goods that need more inputs from a production factor that is rare.