Comparative advantage

In economics, the theory of comparative advantage explains why it can be beneficial for two to trade, even though one of them may be able to produce every kind of item more cheaply than the other. What matters is not the absolute cost of production, but rather the ratio between how easily the two countries can produce different kinds of things. The concept is highly important in modern international trade theory.

Comparative advantage may be compared to absolute advantage. When one entity (be it a company or a country) is able to produce more efficiently than another entity it has an absolute advantage: that is, assuming equal inputs, the entity with an absolute advantage will have a greater output.

Origins of the theory

Comparative advantage was first described by Robert Torrens in 1815 in an essay on the corn trade. He concluded that it was to England's advantage to trade various goods with Poland in return for corn, even though it might be possible to produce that corn more cheaply in England than Poland.

However, the theory is usually attributed to David Ricardo who created a systematic explanation in his 1817 book The Principles of Political Economy and Taxation using an example involving England and Portugal. In Portugal it is possible to produce both wine and cloth with less work than it takes 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 closer to the cost of cloth.

Stanislaw Ulam once challenged Nobel laureate Paul Samuelson to name one theory in all of the social sciences which is both true and nontrivial. Several years later, Samuelson responded with David Ricardo's theory of comparative advantage:

"That it is logically true need not be argued before a mathematician; that it is not trivial is attested by the thousands of important and intelligent men who have never been able to grasp the doctrine for themselves or to believe it after it was explained to them." — Paul Samuelson

Critical analysis of Ricardo's theory

Ricardo's principle relies on a variety of implicit assumptions that are debatable, such as that there is no (or a low) cost for transportation, and that the advantages of increased production outweigh externalities such as environmental contamination or social inequities. It is also necessary that there be restrictions on the flow of capital — otherwise, there would be no incentive to invest in the manufacture of either wine or cloth in England, since both are more costly to produce there.

Opponents of free trade often point out that globalized communications and transportation unavailable in Ricardo's time invalidate the assumption of capital immobility and cause capital to gravitate toward absolute advantage. Another concern is that comparative advantage only works when competition is absolutely perfect. It has also been argued that comparative advantage may reduce economic diversity to risky levels.

Free trade advocates would dissent, however, and say that modernization has decreased transportation and logistics costs through inventions such as the airplane and internet unavailable in Ricardo's time making his theory ever more sound with time, furthermore, despite the increased movement of capital, differences in capacities of production are still wide, in fact, free trade creates a wider gap of production in many areas despite the larger increases it makes in absolute wealth.

In theory, as long a country has one more worker, one more machine, or one extra source of natural resources comparative advantage will still apply.

As to perfect competition, supporters of free trade claim that perfect competition is the result of universal free trade, not its precondition. For free trade advocates, comparative advantage is what a capitalist country must embrace to gain an advantage in an existing mercantalist world.

On a final note, Gottfried Haberler showed in the 1930s that Ricardo's thinking on comparative advantage could also be expressed in neoclassical terms of opportunity cost.

Examples

The following worked examples explain the reasoning behind the theory. In Example 3 all assumptions are italicized for easy reference, and some are explained at the end of the example.

Example 1

Two men land alone in 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 and is 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.

Is it in the interest of either of them to work in isolation? No, specialization and exchange (trade) can benefit both of them.

How should they divide the work? According to comparative, not absolute advantage: the young man must spend more time on the tasks in which he is much better and the old man must concentrate on the tasks in which he is only a little worse. Such an arrangement will increase total production and/or reduce total labour. It will make both of them richer.

Specialisation and exchange will not be possible if there is an absolute resource constraint. If, for example, the amount of fresh water available on the island is enough for one man only there will be war.

Example 2

A Needs 100 P1 and 100 P2
B Needs 100 P1 and 100 P2

A: No trade

Product	Cost	Produced	Cost
P1	10	100	1000
P2	20	100	2000
Net	-	200	3000

B: No trade

Product	Cost	Produced	Cost
P1	15	100	1500
P2	25	100	2500
Net	-	200	4000

A with trade: 100P1 for 56 P2

Product	Cost	Produce	Cost
P1	10	200	2000
P2	20	44	880
Net	-	244	2880

B With trade: 56 P2 for 100 P1

Product	Cost	Produce	Cost
P1	15	0	0
P2	25	156	3900
Net	-	156	3900

So A saved 120 cost units or 4% and B saved 100 cost units or 2.5%. Clearly A gained more from the trade, but both parties experienced growth. Now if B adds some taxes to protect the producers of P1 he can try to get a larger percentage of the trade but his savings goes down as do the overall savings.

Example 3

Suppose for example we have 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: 200 tonnes

Conversely if all of the resources of the countries were allocated to the production of Clothes, output would be:

Northland: 100 tonnes
Southland: 100 tonnes

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

So Southland has an absolute advantage over Northland in the production of Food, and both countries are equally efficient in the production of Clothes. Intuitively it would seem that there is no mutual benefit in trade between the economies. But an examination of the opportunity costs shows something different. For Northland the opportunity cost of producing one tonne of Food is one tonne of Clothes and vice versa. But for Southland the opportunity cost of one tonne of Food is 0.5 tonne of Clothes; and the opportunity cost of one tonne of Clothes is 2 tonnes of Food. Looked at this way, Southland has a comparative advantage in Food production because of its lower opportunity cost of production with respect to Food. And Northland also has a comparative advantage over Southland in the production of Clothes, the opportunity cost of which is lower in Southland with respect to Food than in Northland.

To show that these different opportunity costs can lead to mutual benefit if the countries specialise production and trade, consider the following starting position. Both countries produce and consume only domestically. The volumes are:

**Production and consumption before trade**
	Food	Clothes
Northland	50	50
Southland	100	50
World total	150	100

We now examine the consequences of trade between the two countries. 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. But 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. It follows that the actual 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 countries specialise completely in the goods in which they have comparative advantage, their outputs will be:

**Production after trade**
	Food	Clothes
Northland	0	100
Southland	200	0
World total	200	100

Note that world production of Food had increased and Clothing production has 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	125	50
World total	200	100

Northland has traded 50 tonnes of Clothing for 75 tonnes of Food. Both countries have benefited. In fact, both countries are now consuming at points outside their production possibility frontiers.

Assumptions in Example 3

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? Capital includes production technology and know-how. If it can be moved between countries then the production capabilities of the countries will change. Similarly the movement of labour will change that factor cost and productivity. Perfect transnational mobility of factors of production would invalidate comparative advantage. Imperfect transnational mobility reduces the mutual benefit of trade.
Perfect competition - this is a standard assumption that allows perfectly efficient allocation of productive resources in an idealized free market.

More complexities

While the Ricardian model has only one input, we could extend the model both increasing the number of goods from two goods to n goods and by allowing the productivity coefficient to vary.

References

Hardwick, Khan and Langmead (1990) An introduction to modern economics - 3rd Edn
O'Sulivan, A. & Shefferin S.M. (2003). Economics. Principles & Tools.

External links

David Ricardo's The Principles of Trade and Taxation (original source text)
Ricardo's Difficult Idea, an economist's exploration of why non-economists don't understand and won't take seriously the idea of comparative advantage
Further study notes on comparative advantage
The Ricardian Model of Competitive Advantage
J.G. Hülsmann Capital Exports and Free Trade An explanation of why the immobility of capital is NOT an essential condition

International economics | International trade | Economic theories

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