Салыстырмалы артықшылық: экономикалық үстемдік принципі

Lower relative opportunity cost in producing a good
Comparative advantage in an economic model is the advantage over others in producing a particular good. A good can be produced at a lower relative opportunity cost or autarky price, i. e. at a lower relative marginal cost prior to trade. Comparative advantage describes the economic reality of the work gains from trade for individuals, firms, or nations, which arise from differences in their factor endowments or technological progress. David Ricardo developed the classical theory of comparative advantage in 1817 to explain why countries engage in international trade even when one country's workers are more efficient at producing every single good than workers in other countries. He demonstrated that if two countries capable of producing two commodities engage in the free market (albeit with the assumption that the capital and labour do not move internationally), then each country will increase its overall consumption by exporting the good for which it has a comparative advantage while importing the other good, provided that there exist differences in labor productivity between both countries. Widely regarded as one of the most powerful yet counter intuitive insights in economics, Ricardo's theory implies that comparative advantage rather than absolute advantage is responsible for much of international trade.

Terms of trade is the rate at which one good could be traded for another. If both countries specialize in the good for which they have a comparative advantage then trade, the terms of trade for a good (that benefit both entities) will fall between each entities opportunity costs. In the example above one unit of cloth would trade for between units of wine and units of wine.

In 1930 Austrian American economist Gottfried Haberler detached the doctrine of comparative advantage from Ricardo's labor theory of value and provided a modern opportunity cost formulation. Haberler's reformulation of comparative advantage revolutionized the theory of international trade and laid the conceptual groundwork of modern trade theories. Haberler's innovation was to reformulate the theory of comparative advantage such that the value of good X is measured in terms of the forgone units of production of good Y rather than the labor units necessary to produce good X, as in the Ricardian formulation. Haberler implemented this opportunity cost formulation of comparative advantage by introducing the concept of a production possibility curve into international trade theory.

Since 1817, economists have attempted to generalize the Ricardian model and derive the principle of comparative advantage in broader settings, most notably in the neoclassical specific factors Ricardo Viner (which allows for the model to include more factors than just labour) and factor proportions Heckscher–Ohlin models. Subsequent developments in the new trade theory, motivated in part by the empirical shortcomings of the H–O model and its inability to explain intra industry trade, have provided an explanation for aspects of trade that are not accounted for by comparative advantage. Nonetheless, economists like Alan Deardorff, Avinash Dixit, Gottfried Haberler, and Victor D. Norman have responded with weaker generalizations of the principle of comparative advantage, in which countries will only tend to export goods for which they have a comparative advantage.

In both the Ricardian and H–O models, the comparative advantage theory is formulated for a 2 countries/2 commodities case. It can be extended to a 2 countries/many commodities case, or a many countries/2 commodities case. Adding commodities in order to have a smooth continuum of goods is the major insight of the seminal paper by Dornbusch, Fisher, and Samuelson. In fact, inserting an increasing number of goods into the chain of comparative advantage makes the gaps between the ratios of the labor requirements negligible, in which case the three types of equilibria around any good in the original model collapse to the same outcome. It notably allows for transportation costs to be incorporated, although the framework remains restricted to two countries. But in the case with many countries (more than 3 countries) and many commodities (more than 3 commodities), the notion of comparative advantage requires a substantially more complex formulation.

Skeptics of comparative advantage have underlined that its theoretical implications hardly hold when applied to individual commodities or pairs of commodities in a world of multiple commodities. Deardorff argues that the insights of comparative advantage remain valid if the theory is restated in terms of averages across all commodities. His models provide multiple insights on the correlations between vectors of trade and vectors with relative autarky price measures of comparative advantage. "Deardorff's general law of comparative advantage" is a model incorporating multiple goods which takes into account tariffs, transportation costs, and other obstacles to trade.

Recently, Y. Shiozawa succeeded in constructing a theory of international value in the tradition of Ricardo's cost of production theory of value. This was based on a wide range of assumptions: Many countries; Many commodities; Several production techniques for a product in a country; Input trade (intermediate goods are freely traded); Durable capital goods with constant efficiency during a predetermined lifetime; No transportation cost (extendable to positive cost cases). In a famous comment, McKenzie pointed that "A moment's consideration will convince one that Lancashire would be unlikely to produce cotton cloth if the cotton had to be grown in England." However, McKenzie and later researchers could not produce a general theory which includes traded input goods because of the mathematical difficulty. As John Chipman points it, McKenzie found that "introduction of trade in intermediate product necessitates a fundamental alteration in classical analysis." Durable capital goods such as machines and installations are inputs to the productions in the same title as part and ingredients. In view of the new theory, no physical criterion exists. Deardorff examines 10 versions of definitions in two groups but could not give a general formula for the case with intermediate goods.

Comparative advantage is a theory about the benefits that specialization and trade would bring, rather than a strict prediction about actual behavior. (In practice, governments restrict international trade for a variety of reasons; under Ulysses S. Grant, the US postponed opening up to free trade until its industries were up to strength, following the example set earlier by Britain.) Nonetheless there is a large amount of empirical work testing the predictions of comparative advantage. The empirical works usually involve testing predictions of a particular model. For example, the Ricardian model predicts that technological differences in countries result in differences in labor productivity. The differences in labor productivity in turn determine the comparative advantages across different countries. Testing the Ricardian model for instance involves looking at the relationship between relative labor productivity and international trade patterns. A country that is relatively efficient in producing shoes tends to export shoes.

Assessing the validity of comparative advantage on a global scale with the examples of contemporary economies is analytically challenging because of the multiple factors driving globalization: indeed, investment, migration, and technological change play a role in addition to trade. Even if we could isolate the workings of open trade from other processes, establishing its causal impact also remains complicated: it would require a comparison with a counterfactual world without open trade. Considering the durability of different aspects of globalization, it is hard to assess the sole impact of open trade on a particular economy. Daniel Bernhofen and John Brown have attempted to address this issue, by using a natural experiment of a sudden transition to open trade in a market economy. They focus on the case of Japan. The Japanese economy indeed developed over several centuries under autarky and a quasi isolation from international trade but was, by the mid 19th century, a sophisticated market economy with a population of 30 million. Under Western military pressure, Japan opened its economy to foreign trade through a series of unequal treaties. In 1859, the treaties limited tariffs to 5% and opened trade to Westerners. Considering that the transition from autarky, or self sufficiency, to open trade was brutal, few changes to the fundamentals of the economy occurred in the first 20 years of trade. The general law of comparative advantage theorizes that an economy should, on average, export goods with low self sufficiency prices and import goods with high self sufficiency prices. Bernhofen and Brown found that by 1869, the price of Japan's main export, silk and derivatives, saw a 100% increase in real terms, while the prices of numerous imported goods declined of 30 75%. In the next decade, the ratio of imports to gross domestic product reached 4%.

Another important way of demonstrating the validity of comparative advantage has consisted in 'structural estimation' approaches. These approaches have built on the Ricardian formulation of two goods for two countries and subsequent models with many goods or many countries. The aim has been to reach a formulation accounting for both multiple goods and multiple countries, in order to reflect real world conditions more accurately. Jonathan Eaton and Samuel Kortum underlined that a convincing model needed to incorporate the idea of a 'continuum of goods' developed by Dornbusch et al. for both goods and countries. They were able to do so by allowing for an arbitrary (integer) number i of countries, and dealing exclusively with unit labor requirements for each good (one for each point on the unit interval) in each country (of which there are i).

Two of the first tests of comparative advantage were by MacDougall (1951, 1952). A prediction of a two country Ricardian comparative advantage model is that countries will export goods where output per worker (i. e. productivity) is higher. That is, we expect a positive relationship between output per worker and the number of exports. MacDougall tested this relationship with data from the US and UK, and did indeed find a positive relationship. The statistical test of this positive relationship was replicated with new data by Stern (1962) and Balassa (1963). Dosi et al. (1988) conducted a book length empirical examination that suggests that international trade in manufactured goods is largely driven by differences in national technological competencies. One critique of the textbook model of comparative advantage is that there are only two goods. The results of the model are robust to this assumption. Dornbusch et al. (1977) generalized the theory to allow for such a large number of goods as to form a smooth continuum. Based in part on these generalizations of the model, Davis (1995) provides a more recent view of the Ricardian approach to explain trade between countries with similar resources. More recently, Golub and Hsieh (2000) presents modern statistical analysis of the relationship between relative productivity and trade patterns, which finds reasonably strong correlations, and Nunn (2007) finds that countries that have greater enforcement of contracts specialize in goods that require relationship specific investments. Taking a broader perspective, there has been work about the benefits of international trade. Zimring & Etkes (2014) finds that the Blockade of the Gaza Strip, which substantially restricted the availability of imports to Gaza, saw labor productivity fall by 20% in three years. Markusen et al. (1994) reports the effects of moving away from autarky to free trade during the Meiji Restoration, with the result that national income increased by up to 65% in 15 years.

Several arguments have been advanced against using comparative advantage as a justification for advocating free trade, and they have gained an audience among economists. James Brander and Barbara Spencer demonstrated how, in a strategic setting where a few firms compete for the world market, export subsidies and import restrictions can keep foreign firms from competing with national firms, increasing welfare in the country implementing these so called strategic trade policies. There are some economists who dispute the claims of the benefit of comparative advantage. James K. Galbraith has stated that "free trade has attained the status of a god" and that " none of the world's most successful trading regions, including Japan, Korea, Taiwan, and now mainland China, reached their current status by adopting neoliberal trading rules." He argues that comparative advantage relies on the assumption of constant returns, which he states is not generally the case. According to Galbraith, nations trapped into specializing in agriculture are condemned to perpetual poverty, as agriculture is dependent on land, a finite non increasing natural resource.