International trade is exchange of capital, goods, and services across international borders or territories.. In most countries, it represents a significant share of gross domestic product (GDP). While international trade has been present throughout much of history (see Silk Road, Amber Road), its economic, social, and political importance has been on the rise in recent centuries. Industrialization, advanced transportation, globalization, multinational corporations, and outsourcing are all having a major impact on the international trade system. Increasing international trade is crucial to the continuance of globalization. Without international trade, nations would be limited to the goods and services produced within their own borders. International trade is in principle not different from domestic trade as the motivation and the behavior of parties involved in a trade do not change fundamentally regardless of whether trade is across a border or not. The main difference is that international trade is typically more costly than domestic trade. The reason is that a border typically imposes additional costs such as tariffs, time costs due to border delays and costs associated with country differences such as language, the legal system or culture. Another difference between domestic and international trade is that factors of production such as capital and labour are typically more mobile within a country than across countries. Thus international trade is mostly restricted to trade in goods and services, and only to a lesser extent to trade in capital, labor or other factors of production. Then trade in goods and services can serve as a substitute for trade in factors of production. Instead of importing a factor of production, a country can import goods that make intensive use of the factor of production and are thus embodying the respective factor. An example is the import of labor-intensive goods by the United States from China. Instead of importing Chinese labor the United States is importing goods from China that were produced with Chinese labor. International trade is also a branch of economics, which, together with international finance, forms the larger branch of international economics.
The Ricardian model focuses on comparative advantage and is perhaps the most important concept in international trade theory. In a Ricardian model, countries specialize in producing what they produce best. Unlike other models, the Ricardian framework predicts that countries will fully specialize instead of producing a broad array of goods. Also, the Ricardian model does not directly consider factor endowments, such as the relative amounts of labor and capital within a country. The main merit of Ricardin model is that it assumes technology differences between countries. Technology gap is easily included in the Ricardian and Ricardo-Sraffa model (See the next subsection). The Ricardian model makes the following assumptions:
1. Labor is the only primary input to production (labor is considered to be the ultimate source of value). 2. Constant Marginal Product of Labor (MPL) (Labor productivity is constant, constant returns to scale, and simple technology.) 3. Limited amount of labor in the economy
4. Labor is perfectly mobile among sectors but not internationally. 5. Perfect competition (price-takers).
The Ricardian model measures in the short-run, therefore technology differs internationally. This supports the fact that countries follow their comparative advantage and allows for specialization.
Modern development of the Ricardian model
The Ricardian trade model was studied by Graham, Jones, McKenzie and others. All the theories excluded intermediate goods, or traded input goods such as materials and capital goods. McKenzie(1954), Jones(1961) and Samuelson(2001)emphasized that considerable gains from trade would be lost once intermediate goods were excluded from trade. In a...