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In economics, the law of comparative advantage refers to the ability of a party (an individual, a firm, or a country) to produce a particular good or service at a lower opportunity cost than another party. It is the ability to produce a product most efficiently given all the other products that could be produced. It can be contrasted with absolute advantage which refers to the ability of a party to produce a particular good at a lower absolute cost than another.

Comparative advantage explains how trade can create value for both parties even when one can produce all goods with fewer resources than the other. The net benefits of such an outcome are called gains from trade.

Origins of the theory

Comparative advantage was first described by Robert Torrens in 1815 in an essay on the Corn Laws. He concluded it was to Englandmarker's advantage to trade with Portugalmarker in return for grain, even though it might be possible to produce that grain more cheaply in England than Portugal.

However the term is usually attributed to David Ricardo who explained it in his 1817 book On the Principles of Political Economy and Taxation in an example involving England and Portugal. In Portugal it is possible to produce both wine and cloth with less labor than it would take to produce the same quantities in England. However the relative costs of producing those two goods are different in the two countries. In England it is very hard to produce wine, and only moderately difficult to produce cloth. In Portugal both are easy to produce. Therefore while it is cheaper to produce cloth in Portugal than England, it is cheaper still for Portugal to produce excess wine, and trade that for English cloth. Conversely England benefits from this trade because its cost for producing cloth has not changed but it can now get wine at a lower price, closer to the cost of cloth. The conclusion drawn is that each country can gain by specializing in the good where it has comparative advantage, and trading that good for the other.


The following hypothetical examples explain the reasoning behind the theory. In Example 2 all assumptions are italicized for easy reference, and some are explained at the end of the example.

Example 1

Two men live alone on an isolated island. To survive they must undertake a few basic economic activities like water carrying, fishing, cooking and shelter construction and maintenance. The first man is young, strong, and educated. He is also, faster, better, more productive at everything. He has an absolute advantage in all activities. The second man is old, weak, and uneducated. He has an absolute disadvantage in all economic activities. In some activities the difference between the two is great; in others it is small.

Despite the fact that the younger man has absolute advantage in all activities, it is not in the interest of either of them to work in isolation since they both can benefit from specialization and exchange. If the two men divide the work according to comparative advantage then the young man will specialize in tasks at which he is most productive, while the older man will concentrate on tasks where his productivity is only a little less than that of the young man. Such an arrangement will increase total production for a given amount of labor supplied by both men and it will benefit both of them.

Example 2

Suppose there are two countries of equal size, Northland and Southland, that both produce and consume two goods, Food and Clothes. The productive capacities and efficiencies of the countries are such that if both countries devoted all their resources to Food production, output would be as follows:
  • Northland: 100 tonnes
  • Southland: 400 tonnes

If all the resources of the countries were allocated to the production of Clothes, output would be:
  • Northland: 100 tonnes
  • Southland: 200 tonnes

Assuming each has constant opportunity costs of production between the two products and both economies have full employment at all times. All factors of production are mobile within the countries between clothing and food industries, but are immobile between the countries. The price mechanism must be working to provide perfect competition.

Southland has an absolute advantage over Northland in the production of Food and Clothing. There seems to be no mutual benefit in trade between the economies, as Southland is more efficient at producing both products. The opportunity costs shows otherwise. Northland's opportunity cost of producing one tonne of Food is one tonne of Clothes and vice versa. Southland's opportunity cost of one tonne of Food is 0.5 tonne of Clothes. The opportunity cost of one tonne of Clothes is 2 tonnes of Food. Southland has a comparative advantage in food production, because of its lower opportunity cost of production with respect to Northland. Northland has a comparative advantage over Southland in the production of clothes, the opportunity cost of which is higher in Southland with respect to Food than in Northland.

To show these different opportunity costs lead to mutual benefit if the countries specialize production and trade, consider the countries produce and consume only domestically. The volumes are:

Production and consumption before trade
Food Clothes
Northland 50 50
Southland 200 100
TOTAL 250 150

This example includes no formulation of the preferences of consumers in the two economies which would allow the determination of the international exchange rate of Clothes and Food. Given the production capabilities of each country, in order for trade to be worthwhile Northland requires a price of at least one tonne of Food in exchange for one tonne of Clothes; and Southland requires at least one tonne of Clothes for two tonnes of Food. The exchange price will be somewhere between the two. The remainder of the example works with an international trading price of one tonne of Food for 2/3 tonne of Clothes.

If both specialize in the goods in which they have comparative advantage, their outputs will be:

Production after trade
Food Clothes
Northland 0 100
Southland 300 50
TOTAL 300 150

World production of food increased. Clothing production remained the same. Using the exchange rate of one tonne of Food for 2/3 tonne of Clothes, Northland and Southland are able to trade to yield the following level of consumption:

Consumption after trade
Food Clothes
Northland 75 50
Southland 225 100
World total 300 150

Northland traded 50 tonnes of Clothing for 75 tonnes of Food. Both benefited, and now consume at points outside their production possibility frontiers.

Assumptions in Example 2

  • Two countries, two goods - the theory is no different for larger numbers of countries and goods, but the principles are clearer and the argument easier to follow in this simpler case.
  • Equal size economies - again, this is a simplification to produce a clearer example.
  • Full employment - if one or other of the economies has less than full employment of factors of production, then this excess capacity must usually be used up before the comparative advantage reasoning can be applied.
  • Constant opportunity costs - a more realistic treatment of opportunity costs the reasoning is broadly the same, but specialization of production can only be taken to the point at which the opportunity costs in the two countries become equal. This does not invalidate the principles of comparative advantage, but it does limit the magnitude of the benefit.
  • Perfect mobility of factors of production within countries - this is necessary to allow production to be switched without cost. In real economies this cost will be incurred: capital will be tied up in plant (sewing machines are not sowing machines) and labour will need to be retrained and relocated. This is why it is sometimes argued that 'nascent industries' should be protected from fully liberalised international trade during the period in which a high cost of entry into the market (capital equipment, training) is being paid for.
  • Immobility of factors of production between countries - why are there different rates of productivity? The modern version of comparative advantage (developed in the early twentieth century by the Swedish economists Eli Heckscher and Bertil Ohlin) attributes these differences to differences in nations' factor endowments. A nation will have comparative advantage in producing the good that uses intensively the factor it produces abundantly. For example: suppose the US has a relative abundance of capital and India has a relative abundance of labor. Suppose further that cars are capital intensive to produce, while cloth is labor intensive. Then the US will have a comparative advantage in making cars, and India will have a comparative advantage in making cloth. If there is international factor mobility this can change nations' relative factor abundance. The principle of comparative advantage still applies, but who has the advantage in what can change.
  • Negligible Transport Cost - Cost is not a cause of concern when countries decided to trade. It is ignored and not factored in.
  • Assume that half the resources are used to produce each good in each country. This takes place before specialization
  • Perfect competition - this is a standard assumption that allows perfectly efficient allocation of productive resources in an idealized free market.

Example 3

The economist Paul Samuelson provided another well known example in his Economics. Suppose that in a particular city the best lawyer happens also to be the best secretary, that is he would be the most productive lawyer and he would also be the best secretary in town. However, if this lawyer focused on the task of being an attorney and, instead of pursuing both occupations at once, employed a secretary, both the output of the lawyer and the secretary would increase.

Effects on the economy

Conditions that maximize comparative advantage do not automatically resolve trade deficits. In fact, in many real world examples where comparative advantage is attainable may in fact require a trade deficit. For example, the amount of goods produced can be maximized, yet it may involve a net transfer of wealth from one country to the other, often because economic agents have widely different rates of saving.

As the markets change over time, the ratio of goods produced by one country versus another variously changes while maintaining the benefits of comparative advantage. This can cause national currencies to accumulate into bank deposits in foreign countries where a separate currency is used.

Macroeconomic monetary policy is often adapted to address the depletion of a nation's currency from domestic hands by the issuance of more money, leading to a wide range of historical successes and failures.


Free mobility of capital in a globalized world

Ricardo explicitly bases his argument on an assumed immobility of capital:

" ... if capital freely flowed towards those countries where it could be most profitably employed, there could be no difference in the rate of profit, and no other difference in the real or labour price of commodities, than the additional quantity of labour required to convey them to the various markets where they were to be sold."

He explains why from his point of view (anno 1817) this is a reasonable assumption:"Experience, however, shows, that the fancied or real insecurity of capital, when not under the immediate control of its owner, together with the natural disinclination which every man has to quit the country of his birth and connexions, and entrust himself with all his habits fixed, to a strange government and new laws, checks the emigration of capital."

Some scholars, notably Herman Daly, an American ecological economist and professor at the School of Public Policy of University of Maryland, have voiced concern over the applicability of Ricardo's theory of comparative advantage in light of a perceived increase in the mobility of capital:"International trade (governed by comparative advantage) becomes, with the introduction of free capital mobility, interregional trade (governed by Absolute advantage)."

See also


  1. Ricardo (1817). On the Principles of Political Economy and Taxation. London, Chapter 7


  • Chang, Ha-Joon (2002). Kicking Away the Ladder: Development Strategy in Historical Perspective, Anthem Press.
  • Chang, Ha-Joon (2008). Bad Samaritans: The Myth of Free Trade and the Secret History of Capitalism, Bloomsbury Press.
  • Ronald Findlay (1987). "comparative advantage," The New Palgrave: A Dictionary of Economics, v. 1, pp. 514-17.
  • Hardwick, Khan and Langmead (1990). An Introduction to Modern Economics - 3rd Edn
  • A. O'Sullivan & S.M. Sheffrin (2003). Economics. Principles & Tools.

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