Mozart effect

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The Mozart effect can refer to:

• A set of research results indicating that listening to Mozart's music may induce a short-term improvement on the performance of certain kinds of mental tasks known as "spatial-temporal reasoning";
• Popularized versions of the hypothesis, which suggest that "listening to Mozart makes you smarter", or that early childhood exposure to classical music has a beneficial effect on mental development;
• A US trademark for a set of commercial recordings and related materials, which are claimed to harness the effect for a variety of purposes. The trademark owner, Don Campbell, Inc., claims benefits far beyond improving spatio-temporal reasoning or raising intelligence, defining the mark as "an inclusive term signifying the transformational powers of music in health, education, and well-being."

The term was first coined by Alfred A. Tomatis who used Mozart's music as the listening stimulus in his work attempting to cure a variety of disorders. The approach has been popularized in Don Campbell's book, The Mozart Effect, which is based on an experiment published in Nature suggesting that listening to Mozart temporarily boosted scores on one portion of the IQ test. As a result, the United States' Governor of Georgia, Zell Miller, proposed a budget to provide every child born in Georgia with a CD of classical music.

Because of bad methodology in the first experiment and lack of replication, the Mozart effect is now believed to be a myth.

Alfred A. Tomatis

The concept of the "Mozart effect" was described by French researcher Dr. Alfred A. Tomatis in his 1991 book Pourquoi Mozart? (Why Mozart?). He used the music of Mozart in his efforts to "retrain" the ear, and believed that listening to the music presented at differing frequencies helped the ear, and promoted healing and the development of the brain.

Rauscher et al. 1993 study

Frances Rauscher, Gordon Shaw, and Catherine Ky (1993) investigated the effect of listening to music by Mozart on spatial reasoning, and the results were published in Nature. They gave research participants one of three standard tests of abstract spatial reasoning after they had experienced each of three listening conditions: the Sonata for Two Pianos in D major, K. 448 by Mozart, verbal relaxation instructions, and silence. They found a temporary enhancement of spatial-reasoning, as measured by spatial-reasoning sub tasks of the Stanford-Binet IQ test. Rauscher et al. show that the enhancing effect of the music condition is only temporary: no student had effects extending beyond the 15-minute period in which they were tested. The study makes no statement of an increase in IQ in general (because IQ was never measured).

Popularization

While Rauscher et al. only showed an increase in "spatial intelligence", the results were popularly interpreted as an increase in general IQ. This misconception, and the fact that the music used in the study was by Mozart, had an obvious appeal to those who valued this music; the Mozart effect was thus widely reported. In 1994, New York Times music columnist Alex Ross wrote in a light-hearted article, "researchers [Rauscher and Shaw] have determined that listening to Mozart actually makes you smarter", and presented this as the final piece of evidence that Mozart has dethroned Beethoven as "the world's greatest composer. " A 1997 Boston Globe article mentioned some of the Rauscher and Shaw results. It described one study in which three- and four-year-olds who were given eight months of private piano lessons scored 30% higher on tests of spatio-temporal reasoning than control groups given computer lessons, singing lessons, and no training. 

The 1997 book by Don Campbell, The Mozart Effect: Tapping the Power of Music to Heal the Body, Strengthen the Mind, and Unlock the Creative Spirit, discusses the theory that listening to Mozart (especially the piano concertos) may temporarily increase one's IQ and produce many other beneficial effects on mental function. Campbell recommends playing specially selected classical music to infants, in the expectation that it will benefit their mental development.

After The Mozart Effect, Campbell wrote a follow-up book, The Mozart Effect For Children, and created related products. Among these are collections of music that he states harness the Mozart effect to enhance "deep rest and rejuvenation", "intelligence and learning", and "creativity and imagination". Campbell defines the term as "an inclusive term signifying the transformational powers of music in health, education, and well-being. It represents the general use of music to reduce stress, depression, or anxiety; induce relaxation or sleep; activate the body; and improve memory or awareness. Innovative and experimental uses of music and sound can improve listening disorders, dyslexia, attention deficit disorder, autism, and other mental and physical disorders and diseases".

These theories are controversial. The relationship of sound and music (both played and listened to) for cognitive function and various physiological metrics has been explored in studies with no definitive results.

Political impact

The political impact of the theory was demonstrated on January 13, 1998, when Zell Miller, governor of Georgia, announced that his proposed state budget would include $105,000 a year to provide every child born in Georgia with a tape or CD of classical music. Miller stated "No one questions that listening to music at a very early age affects the spatial-temporal reasoning that underlies math and engineering and even chess." Miller played legislators some of Beethoven's "Ode to Joy" on a tape recorder and asked "Now, don't you feel smarter already?" Miller asked Yoel Levi, music director of the Atlanta Symphony, to compile a collection of classical pieces that should be included. State representative Homer DeLoach said "I asked about the possibility of including some Charlie Daniels or something like that, but they said they thought the classical music has a greater positive impact. Having never studied those impacts too much, I guess I'll just have to take their word for that."

Subsequent research and meta-analyses

While some supportive reports have been published, studies with positive results have tended to be associated with any form of music that has energetic and positive emotional qualities. Moreover, the intellectual benefits of enhanced mood and arousal are not restricted to spatial-temporal reasoning, but extend to speed of processing and creative problem solving. Among children, some studies suggest no effect on IQ or spatial ability, whereas others suggest that the effect can be elicited with energetic popular music that the children enjoy. The weight of subsequent evidence supports either a null effect, or short-term effects related to increases in mood and arousal, with mixed results published after the initial report in Nature.

In 1999 a major challenge was raised to the existence of the Mozart effect by two teams of researchers. In a pair of papers published together under the title "Prelude or Requiem for the 'Mozart Effect'?" Chabris reported a meta-analysis demonstrating that "any cognitive enhancement is small and does not reflect any change in IQ or reasoning ability in general, but instead derives entirely from performance on one specific type of cognitive task and has a simple neuropsychological explanation", called "enjoyment arousal". For example, he cites a study that found that "listening either to Mozart or to a passage from a Stephen King story enhanced subjects' performance in paper folding and cutting (one of the tests frequently employed by Rauscher and Shaw) but only for those who enjoyed what they heard". Steele et. al. found that "listening to Mozart produced a 3-point increase relative to silence in one experiment and a 4-point decrease in the other experiment". In another study, the effect was replicated with the original Mozart music, but eliminated when the tempo was slowed down and major chords were replaced by minor chords.

Another meta-analysis by Pietschnig, Voracek, and Formann (2010) combined results of 39 studies to answer the question as to whether or not the Mozart Effect exists. They concluded that there is little evidence to support the Mozart effect, as shown by small effect sizes. However, the most striking finding in this meta-analysis is the significantly larger effects published in studies affiliated with Rauscher or Rideout, with effect sizes more than three times higher for published studies affiliated with these founding members of the Mozart Effect. These systematic moderating effects due to lab affiliation call into question the existence of a Mozart Effect. In addition, this study also found strong evidence supporting a confounding publication bias when effect sizes of samples who listened to Mozart are compared to samples not exposed to a stimulus.

Despite implementing Rauscher, Shaw, and Ky's (1995) suggestions of three key components that must be present to replicate the Mozart Effect, McCutcheon (2000) still failed to reproduce the Mozart Effect in a study with 36 adults. These conditions were: to ensure a task that taps into spatial components of mental imagery; a research design that does not include a pretest to avoid ceiling effects; a musical composition that is complex rather than repetitive and simple. Regardless of listening to classical music, jazz or silence, the study did not yield a significant effect on spatial reasoning performance.

The Mozart Effect is likely just an artifact of arousal and heightened mood. Arousal is the confounding variable that mediates the relationship between spatial ability and music that defines the Mozart Effect. The "neural resonance" theory of Rauscher and colleagues which contends that Mozart's music primes the neural pathways of spatial reasoning has been widely criticized.

Government bodies also became involved in analysing the wealth (some 300+ articles as of 2005) of reports. A German report concluded, for instance, that "... passively listening to Mozart — or indeed any other music you enjoy — does not make you smarter. But more studies should be done to find out whether music lessons could raise your child's IQ in the long term".

Popular presentations of the "Mozart effect", including Alex Ross's comment that "listening to Mozart actually makes you smarter" and Zell Miller's "don't you feel smarter" query to the Georgia legislature, almost always tie it to "intelligence." Rauscher, one of the original researchers, has disclaimed this idea. In a 1999 reply to an article challenging the effect, published along with the article, she wrote (emphasis added):

Our results on the effects of listening to Mozart's Sonata for Two Pianos in D Major K. 448 on spatial–temporal task performance have generated much interest but several misconceptions, many of which are reflected in attempts to replicate the research. The comments by Chabris and Steele et al. echo the most common of these: that listening to Mozart enhances intelligence. We made no such claim. The effect is limited to spatial–temporal tasks involving mental imagery and temporal ordering.

On efforts like Miller's budget proposal, and the press attention surrounding the effect, Rauscher has said, "I don't think it can hurt. I'm all for exposing children to wonderful cultural experiences. But I do think the money could be better spent on music education programs."

Many scholars in the psychological community now view the claim that playing classical music to children can boost their intelligence to be a "myth." Emory University psychologist Scott Lilienfeld ranks Mozart Effect as number six in his book 50 Great Myths of Popular Psychology.

Health benefits

Music has been evaluated to see if it has other properties. The April 2001 edition of Journal of the Royal Society of Medicine assessed the possible health benefits of the music of Mozart. John Jenkins played Sonata K.448 to patients with epilepsy and found a decrease in epileptiform activity. According to the British Epilepsy Organization, research has suggested that apart from Mozart's K.448 and Piano Concerto No. 23 (K. 488), only one other piece of music has been found to have a similar effect; a song by the Greek composer Yanni, entitled "Acroyali/Standing in Motion" (version from Yanni Live at the Acropolis performed at the Acropolis). It was determined to have the "Mozart effect", by the Journal of the Royal Society of Medicine because it was similar to Mozart's K.448 in tempo, structure, melodic and harmonic consonance and predictability.

Other uses of Mozart's music

While it is clear that exposure to Mozart does not raise IQ, studies of the effects of music have explored as diverse areas as its links to seizure onset or research in animals suggesting that even exposure in-utero in rats improves their maze learning. The original claim continues to influence public life. For instance a German sewage treatment plant plays Mozart music to break down the waste faster, reports the UK Guardian. Anton Stucki, chief operator of the Treuenbrietzen plant was quoted as saying, "We think the secret is in the vibrations of the music, which penetrate everything—including the water, the sewage and the cells."

Comparative advantage

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The law of comparative advantage describes how, under free trade, an agent will produce more of and consume less of a good for which they have a comparative advantage.

In an economic model, agents have a comparative advantage over others in producing a particular good if they can produce that good 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. (One should not compare the monetary costs of production or even the resource costs (labor needed per unit of output) of production. Instead, one must compare the opportunity costs of producing goods across countries).

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, 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.

Classical theory and David Ricardo's formulation

Adam Smith first alluded to the concept of absolute advantage as the basis for international trade in 1776, in The Wealth of Nations:

If a foreign country can supply us with a commodity cheaper than we ourselves can make it, better buy it off them with some part of the produce of our own industry employed in a way in which we have some advantage. The general industry of the country, being always in proportion to the capital which employs it, will not thereby be diminished [...] but only left to find out the way in which it can be employed with the greatest advantage.

Writing several decades after Smith in 1808, Robert Torrens articulated a preliminary definition of comparative advantage as the loss from the closing of trade:

[I]f I wish to know the extent of the advantage, which arises to England, from her giving France a hundred pounds of broadcloth, in exchange for a hundred pounds of lace, I take the quantity of lace which she has acquired by this transaction, and compare it with the quantity which she might, at the same expense of labour and capital, have acquired by manufacturing it at home. The lace that remains, beyond what the labour and capital employed on the cloth, might have fabricated at home, is the amount of the advantage which England derives from the exchange.

David Ricardo

In 1817, David Ricardo published what has since become known as the theory of comparative advantage in his book On the Principles of Political Economy and Taxation.

Ricardo's example

Graph illustrating Ricardo's example:
In case I (diamonds), each country spends 3600 hours to produce a mixture of cloth and wine.
In case II (squares), each country specializes in its comparative advantage, resulting in greater total output.

In a famous example, Ricardo considers a world economy consisting of two countries, Portugal and England, each producing two goods of identical quality. In Portugal, the a priori more efficient country, it is possible to produce 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 differ between the countries.

Hours of work necessary to produce one unit

Produce Country	Cloth	Wine
England	100	120
Portugal	90	80

In this illustration, England could commit 100 hours of labor to produce one unit of cloth, or produce 5/6 units of wine. Meanwhile, in comparison, Portugal could commit 90 hours of labor to produce one unit of cloth, or produce 9/8 units of wine. So, Portugal possesses an absolute advantage in producing cloth due to fewer labor hours, but England has a comparative advantage in producing cloth due to lower opportunity cost.

In the absence of trade, England requires 220 hours of work to both produce and consume one unit each of cloth and wine while Portugal requires 170 hours of work to produce and consume the same quantities. England is more efficient at producing cloth than wine, and Portugal is more efficient at producing wine than cloth. So, if each country specializes in the good for which it has a comparative advantage, then the global production of both goods increases, for England can spend 220 labor hours to produce 2.2 units of cloth while Portugal can spend 170 hours to produce 2.125 units of wine. Moreover, if both countries specialize in the above manner and England trades a unit of its cloth for 5/6 to 9/8 units of Portugal's wine, then both countries can consume at least a unit each of cloth and wine, with 0 to 0.2 units of cloth and 0 to 0.125 units of wine remaining in each respective country to be consumed or exported. Consequently, both England and Portugal can consume more wine and cloth under free trade than in autarky.

Ricardian model

The Ricardian model is a general equilibrium mathematical model of international trade. Although the idea of the Ricardian model was first presented in the Essay on Profits (a single-commodity version) and then in the Principles (a multi-commodity version) by David Ricardo, the first mathematical Ricardian model was published by William Whewell in 1833. The earliest test of the Ricardian model was performed by G.D.A MacDougall, which was published in Economic Journal of 1951 and 1952.  In the Ricardian model, trade patterns depend on productivity differences.

The following is a typical modern interpretation of the classical Ricardian model. In the interest of simplicity, it uses notation and definitions, such as opportunity cost, unavailable to Ricardo.

The world economy consists of two countries, Home and Foreign, which produce wine and cloth. Labor, the only factor of production, is mobile domestically but not internationally; there may be migration between sectors but not between countries. We denote the labor force in Home by ${\displaystyle \textstyle L}$, the amount of labor required to produce one unit of wine in Home by ${\displaystyle \textstyle a_{LW}}$, and the amount of labor required to produce one unit of cloth in Home by ${\displaystyle \textstyle a_{LC}}$. The total amount of wine and cloth produced in Home are ${\displaystyle Q_{W}}$ and ${\displaystyle Q_{C}}$ respectively. We denote the same variables for Foreign by appending a prime. For instance, ${\displaystyle \textstyle a'_{LW}}$ is the amount of labor needed to produce a unit of wine in Foreign.

We don't know if Home is more productive than Foreign in making cloth. That is, we don't know that ${\displaystyle a_{LC}$. Similarly, we don't know if Home has an absolute advantage in wine. However, we will assume that Home is more relatively productive in cloth than Foreign:

${\displaystyle a_{LC}/a'_{LC}$

Equivalently, we may assume that Home has a comparative advantage in cloth in the sense that it has a lower opportunity cost for cloth in terms of wine than Foreign:

${\displaystyle a_{LC}/a_{LW}$

In the absence of trade, the relative price of cloth and wine in each country is determined solely by the relative labor cost of the goods. Hence the relative autarky price of cloth is ${\displaystyle a_{LC}/a_{LW}}$ in Home and ${\displaystyle a'_{LC}/a'_{LW}}$ in Foreign. With free trade, the price of cloth or wine in either country is the world price ${\displaystyle P_{C}}$ or${\displaystyle P_{W}}$.

Instead of considering the world demand (or supply) for cloth and wine, we are interested in the world relative demand (or relative supply) for cloth and wine, which we define as the ratio of the world demand (or supply) for cloth to the world demand (or supply) for wine. In general equilibrium, the world relative price ${\displaystyle \textstyle P_{C}/P_{W}}$ will be determined uniquely by the intersection of world relative demand ${\displaystyle \textstyle RD}$ and world relative supply ${\displaystyle \textstyle RS}$ curves.

The demand for cloth relative to wine decreases with the relative price of cloth in terms of wine; the supply ${\displaystyle RS}$ of cloth relative to wine increases with relative price. Two relative demand curves ${\displaystyle RD_{1}}$ and ${\displaystyle RD_{2}}$ are drawn for illustrative purposes.

We assume that the relative demand curve reflects substitution effects and is decreasing with respect to relative price. The behavior of the relative supply curve, however, warrants closer study. Recalling our original assumption that Home has a comparative advantage in cloth, we consider five possibilities for the relative quantity supplied at a given price.

• If ${\displaystyle \textstyle P_{C}/P_{W}=a_{LC}/a_{LW}$, then Foreign specializes in wine, for the wage ${\displaystyle P'_{W}/a'_{LW}}$ in the wine sector is greater than the wage ${\displaystyle P'_{C}/a'_{LC}}$ in the cloth sector. However, Home workers are indifferent between working in either sector. As a result, the quantity supplied can take any value.
• If ${\displaystyle \textstyle P_{C}/P_{W}$, then both Home and Foreign specialize in wine, for similar reasons as above, and so the quantity supplied is zero.
• If ${\displaystyle \textstyle a_{LC}/a_{LW}$, then Home specializes in cloth whereas Foreign specializes in wine. The quantity supplied is given by the ratio ${\displaystyle \textstyle {\frac {L/a_{LC}}{L'/a'_{LW}}}}$ of the world production of cloth to the world production of wine.
• If ${\displaystyle \textstyle a_{LC}/a_{LW}$, then both Home and Foreign specialize in cloth. The quantity supplied tends to infinity as the quantity of wine supplied approaches zero.
• If ${\displaystyle \textstyle a_{LC}/a_{LW}$, then Home specializes in cloth while Foreign workers are indifferent between sectors. Again, the relative quantity supplied can take any value.

The blue triangle depicts Home's original production (and consumption) possibilities. By trading, Home can also consume bundles in the pink triangle despite facing the same productions possibility frontier.

As long as the relative demand is finite, the relative price is always bounded by the inequality

${\displaystyle a_{LC}/a_{LW}\leq {P_{C}/P_{W}}\leq {a'_{LC}/a'_{LW}}.}$

In autarky, Home faces a production constraint of the form

${\displaystyle a_{LC}Q_{C}+a_{LW}Q_{W}\leq L,}$

from which it follows that Home's cloth consumption at the production possibilities frontier is

${\displaystyle Q_{C}=L/a_{LC}-(a_{LW}/a_{LC})Q_{W}}$.

With free trade, Home produces cloth exclusively, an amount of which it exports in exchange for wine at the prevailing rate. Thus Home's overall consumption is now subject to the constraint

${\displaystyle a_{LC}Q_{C}+a_{LC}(P_{W}/P_{C})Q_{W}\leq L}$

while its cloth consumption at the consumption possibilities frontier is given by

${\displaystyle Q_{C}=L/a_{LC}-(P_{W}/P_{C})Q_{W}\geq L/a_{LC}-(a_{LW}/a_{LC})Q_{W}}$.

A symmetric argument holds for Foreign. Therefore, by trading and specializing in a good for which it has a comparative advantage, each country can expand its consumption possibilities. Consumers can choose from bundles of wine and cloth that they could not have produced themselves in closed economies.

Terms of 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 ${\displaystyle {\frac {5}{6}}}$ units of wine and ${\displaystyle {\frac {9}{8}}}$ units of wine.

Haberler's opportunity costs formulation

In 1930 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.

Modern theories

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.

Dornbusch et al.'s continuum of goods formulation

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.

Deardorff's general law of comparative advantage

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. What has become to be known as the "Deardorff's general law of comparative advantage" is a model incorporating multiple goods, and which takes into account tariffs, transportation costs, and other obstacles to trade.

Alternative approaches

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. The competitive patterns are determined by the traders trials to find cheapest products in a world. The search of cheapest product is achieved by world optimal procurement. Thus the new theory explains how the global supply chains are formed.

Empirical approach to comparative advantage

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.

Direct test: natural experiment of Japan

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%.

Structural estimation

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).

Earlier empirical work

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 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) conduct 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.

Considerations

Development economics

The theory of comparative advantage, and the corollary that nations should specialize, is criticized on pragmatic grounds within the import substitution industrialization theory of development economics, on empirical grounds by the Singer–Prebisch thesis which states that terms of trade between primary producers and manufactured goods deteriorate over time, and on theoretical grounds of infant industry and Keynesian economics. In older economic terms, comparative advantage has been opposed by mercantilism and economic nationalism. These argue instead that while a country may initially be comparatively disadvantaged in a given industry (such as Japanese cars in the 1950s), countries should shelter and invest in industries until they become globally competitive. Further, they argue that comparative advantage, as stated, is a static theory – it does not account for the possibility of advantage changing through investment or economic development, and thus does not provide guidance for long-term economic development.

Much has been written since Ricardo as commerce has evolved and cross-border trade has become more complicated. Today trade policy tends to focus more on "competitive advantage" as opposed to "comparative advantage". One of the most in-depth research undertakings on "competitive advantage" was conducted in the 1980s as part of the Reagan administration's Project Socrates to establish the foundation for a technology-based competitive strategy development system that could be used for guiding international trade policy.

Criticism

Several arguments have been advanced against using comparative advantage as a justification for advocating free trade, and they have gained an audience among economists. For example, 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.

However, the overwhelming consensus of the economics profession remains that while these arguments against comparative advantage are theoretically valid under certain conditions or assumptions, these assumptions do not usually hold. Thus, these arguments should not be used to guide trade policy. Gregory Mankiw, chairman of the Harvard Economics Department, has stated: ″Few propositions command as much consensus among professional economists as that open world trade increases economic growth and raises living standards.″

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 is based upon the concept of constant returns: the idea that you can double or triple the output of any good simply by doubling or tripling the inputs. But this is not generally the case. For manufactured products, increasing returns, learning, and technical change are the rule, not the exception; the cost of production falls with experience. With increasing returns, the lowest cost will be incurred by the country that starts earliest and moves fastest on any particular line. Potential competitors have to protect their own industries if they wish them to survive long enough to achieve competitive scale." 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. Galbraith summarizes: "Comparative advantage has very little practical use for trade strategy. Diversification, not specialization, is the main path out of underdevelopment, and effective diversification requires a strategic approach to trade policy. It cannot mean walling off the outside world, but it is also a goal not easily pursued under a dogmatic commitment to free trade."

According to historian Cecil Woodham-Smith, Ireland in the 1800s is an example of the dangers of over-specialization. When the union with Great Britain was formed in 1800, Irish textile industries protected by tariffs were exposed to world markets where England had a comparative advantage in technology, experience and scale of operation which devastated the Irish industry. Ireland was forced to specialize in the export of grain while the displaced Irish labor was forced into subsistence farming and relying on the potato for survival. When the potato blight occurred the resulting famine killed at least one million Irish in one of the worst famines in European history. As Woodham-Smith would later comment, "the Irish peasant was told to replace the potato by eating his grain, but Trevelyan once again refused to take any steps to curb the export of food from Ireland. 'Do not encourage the idea of prohibiting exports,' he wrote, on September 3, (1846) 'perfect free trade is the right course'."

Free trade is based on the theory of comparative advantage. The classical and neoclassical formulations of comparative advantage theory differ in the tools they use but share the same basis and logic. Comparative advantage theory says that market forces lead all factors of production to their best use in the economy. It indicates that international free trade would be beneficial for all participating countries as well as for the world as a whole because they could increase their overall production and consume more by specializing according to their comparative advantages. Goods would become cheaper and available in larger quantities. Moreover, this specialization would not be the result of chance or political intent, but would be automatic. However according to non-neoclassical economists, the theory is based on assumptions that are neither theoretically nor empirically valid.

International mobility of capital and labour

The international immobility of labour and capital is essential to the theory of comparative advantage. Without this, there would be no reason for international free trade to be regulated by comparative advantages. Classical and neoclassical economists all assume that labour and capital do not circulate between nations. At the international level, only the goods produced can move freely, with capital and labour trapped in countries. David Ricardo was aware that the international immobility of labour and capital is an indispensable hypothesis. He devoted half of his explanation of the theory to it in his book. He even explained that if labour and capital could move internationally, then comparative advantages could not determine international trade. Ricardo assumed that the reasons for the immobility of the capital would be:

"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 intrust himself with all his habits fixed, to a strange government and new laws"

Neoclassical economists, for their part, argue that the scale of these movements of workers and capital is negligible. They developed the theory of price compensation by factor that makes these movements superfluous. In practice, however, workers move in large numbers from one country to another. Today, labour migration is truly a global phenomenon. And, with the reduction in transport and communication costs, capital has become increasingly mobile and frequently moves from one country to another. Moreover, the neoclassical assumption that factors are trapped at the national level has no theoretical basis and the assumption of factor price equalisation cannot justify international immobility. Moreover, there is no evidence that factor prices are equal worldwide. Comparative advantages cannot therefore determine the structure of international trade.

If they are internationally mobile and the most productive use of factors is in another country, then free trade will lead them to migrate to that country. This will benefit the nation to which they emigrate, but not necessarily the others.

Externalities

An externality is the term used when the price of a product does not reflect its cost or real economic value. The classic negative externality is environmental degradation, which reduces the value of natural resources without increasing the price of the product that has caused them harm. The classic positive externality is technological encroachment, where one company's invention of a product allows others to copy or build on it, generating wealth that the original company cannot capture. If prices are wrong due to positive or negative externalities, free trade will produce sub-optimal results.

For example, goods from a country with lax pollution standards will be too cheap. As a result, its trading partners will import too much. And the exporting country will export too much, concentrating its economy too much in industries that are not as profitable as they seem, ignoring the damage caused by pollution.

On the positive externalities, if an industry generates technological spinoffs for the rest of the economy, then free trade can let that industry be destroyed by foreign competition because the economy ignores its hidden value. Some industries generate new technologies, allow improvements in other industries and stimulate technological advances throughout the economy; losing these industries means losing all industries that would have resulted in the future.

Cross-industrial movement of productive resources

Comparative advantage theory deals with the best use of resources and how to put the economy to its best use. But this implies that the resources used to manufacture one product can be used to produce another object. If they cannot, imports will not push the economy into industries better suited to its comparative advantage and will only destroy existing industries.

For example, when workers cannot move from one industry to another—usually because they do not have the right skills or do not live in the right place—changes in the economy's comparative advantage will not shift them to a more appropriate industry, but rather to unemployment or precarious and unproductive jobs.

Static vs. dynamic gains via international trade

Comparative advantage theory allows for a "static" and not a "dynamic" analysis of the economy. That is, it examines the facts at a single point in time and determines the best response to those facts at that point in time, given our productivity in various industries. But when it comes to long-term growth, it says nothing about how the facts can change tomorrow and how they can be changed in someone's favour. It does not indicate how best to transform factors of production into more productive factors in the future.

According to theory, the only advantage of international trade is that goods become cheaper and available in larger quantities. Improving the static efficiency of existing resources would therefore be the only advantage of international trade. And the neoclassical formulation assumes that the factors of production are given only exogenously. Exogenous changes can come from population growth, industrial policies, the rate of capital accumulation (propensity for security) and technological inventions, among others. Dynamic developments endogenous to trade such as economic growth are not integrated into Ricardo's theory. And this is not affected by what is called "dynamic comparative advantage". In these models, comparative advantages develop and change over time, but this change is not the result of trade itself, but of a change in exogenous factors.

However, the world, and in particular the industrialized countries, are characterized by dynamic gains endogenous to trade, such as technological growth that has led to an increase in the standard of living and wealth of the industrialized world. In addition, dynamic gains are more important than static gains.

Balanced trade and adjustment mechanisms

A crucial assumption in both the classical and neoclassical formulation of comparative advantage theory is that trade is balanced, which means that the value of imports is equal to the value of each country's exports. The volume of trade may change, but international trade will always be balanced at least after a certain adjustment period. The balance of trade is essential for theory because the resulting adjustment mechanism is responsible for transforming the comparative advantages of production costs into absolute price advantages. And this is necessary because it is the absolute price differences that determine the international flow of goods. Since consumers buy a good from the one who sells it cheapest, comparative advantages in terms of production costs must be transformed into absolute price advantages. In the case of floating exchange rates, it is the exchange rate adjustment mechanism that is responsible for this transformation of comparative advantages into absolute price advantages. In the case of fixed exchange rates, neoclassical theory suggests that trade is balanced by changes in wage rates.

So if trade were not balanced in itself and if there were no adjustment mechanism, there would be no reason to achieve a comparative advantage. However, trade imbalances are the norm and balanced trade is in practice only an exception. In addition, financial crises such as the Asian crisis of the 1990s show that balance of payments imbalances are rarely benign and do not self-regulate. There is no adjustment mechanism in practice. Comparative advantages do not turn into price differences and therefore cannot explain international trade flows.

Thus, theory can very easily recommend a trade policy that gives us the highest possible standard of living in the short term but none in the long term. This is what happens when a nation runs a trade deficit, which necessarily means that it goes into debt with foreigners or sells its existing assets to them. Thus, the nation applies a frenzy of consumption in the short term followed by a long-term decline.

International trade as bartering

The assumption that trade will always be balanced is a corollary of the fact that trade is understood as barter. The definition of international trade as barter trade is the basis for the assumption of balanced trade. Ricardo insists that international trade takes place as if it were purely a barter trade, a presumption that is maintained by subsequent classical and neoclassical economists. The quantity of money theory, which Ricardo uses, assumes that money is neutral and neglects the velocity of a currency. Money has only one function in international trade, namely as a means of exchange to facilitate trade.

In practice, however, the velocity of circulation is not constant and the quantity of money is not neutral for the real economy. A capitalist world is not characterized by a barter economy but by a market economy. The main difference in the context of international trade is that sales and purchases no longer necessarily have to coincide. The seller is not necessarily obliged to buy immediately. Thus, money is not only a means of exchange. It is above all a means of payment and is also used to store value, settle debts and transfer wealth. Thus, unlike the barter hypothesis of the comparative advantage theory, money is not a commodity like any other. Rather, it is of practical importance to specifically own money rather than any commodity. And money as a store of value in a world of uncertainty has a significant influence on the motives and decisions of wealth holders and producers.

Using labour and capital to their full potential

Ricardo and later classical economists assume that labour tends towards full employment and that capital is always fully used in a liberalized economy, because no capital owner will leave its capital unused but will always seek to make a profit from it. That there is no limit to the use of capital is a consequence of Jean-Baptiste Say's law, which presumes that production is limited only by resources and is also adopted by neoclassical economists.

From a theoretical point of view, comparative advantage theory must assume that labour or capital is used to its full potential and that resources limit production. There are two reasons for this: the realization of gains through international trade and the adjustment mechanism. In addition, this assumption is necessary for the concept of opportunity costs. If unemployment (or underutilized resources) exists, there are no opportunity costs, because the production of one good can be increased without reducing the production of another good. Since comparative advantages are determined by opportunity costs in the neoclassical formulation, these cannot be calculated and this formulation would lose its logical basis.

If a country's resources were not fully utilized, production and consumption could be increased at the national level without participating in international trade. The whole raison d'être of international trade would disappear, as would the possible gains. In this case, a State could even earn more by refraining from participating in international trade and stimulating domestic production, as this would allow it to employ more labour and capital and increase national income. Moreover, any adjustment mechanism underlying the theory no longer works if unemployment exists.

In practice, however, the world is characterised by unemployment. Unemployment and underemployment of capital and labour are not a short-term phenomenon, but it is common and widespread. Unemployment and untapped resources are more the rule than the exception.