Este es un extracto de un excelente artículo de Paul Krugman. Es un poco avanzado para nuestro curso, pero se los recomiendo como lectura optativa.
RICARDO'S DIFFICULT IDEA
"3. A harder concept than it seems
To a trained economist, the basic Ricardian model seems almost trivial. Two goods, two countries, one productive factor, perfect competition: what could be simpler? Indeed, one of the fierce joys of being an international trade economist is that so many seemingly sophisticated tracts can be revealed as nonsense, so many self-important men unmasked as poseurs, using such a minimalist framework.
And yet if one tries to explain the basic model to a non-economist, it soon becomes clear that it really isn't that simple after all. Teaching the model, to docile students, is one thing (...) but try to explain the model to an adult, especially one who already has opinions about the subject, and you continually find yourself obliged to backtrack, realizing that yet another proposition you thought was obvious actually isn't. Just before this paper was written, I was trying to explain to an editorial writer for a major U.S. newspaper why international trade is probably not the main cause of the country's ills. After a confused interlude, it became clear what one of the blocks was: he just didn't understand, even after being told the numbers, why a situation in which productivity increases were not being shared with workers would necessarily be reflected in a decline in the labor share of income -- and therefore why the stability of that share in practice is a crucial piece of evidence. Eventually I was reduced nearly to baby-talk ("suppose the factory produces 10 tons of cheese, and pays out wages equal in value to 6 tons; now suppose that the workers become more productive and turn out 12 tons of cheese, but that wages haven't changed ..."). This was not a successful conversation: he wanted to talk about global trends, and instead I was teaching him first-grade arithmetic.
That particular confusion is more common than one might expect. But even at a somewhat higher level, there are, I believe, at least three implicit assumptions that underlie the most basic Ricardian model, assumptions that are justified by the whole fabric of economic understanding but are not at all obvious to non-economists. Here they are:
- Wages are determined in a national labor market: The basic Ricardian model envisages a single factor, labor, which can move freely between industries. When one tries to talk about trade with laymen, however, one at least sometimes realizes that they do not think about things that way at all. They think about steelworkers, textile workers, and so on; there is no such thing as a national labor market. It does not occur to them that the wages earned in one industry are largely determined by the wages similar workers are earning in other industries. This has several consequences. First, unless it is carefully explained, the standard demonstration of the gains from trade in a Ricardian model -- workers can earn more by moving into the industries in which you have a comparative advantage -- simply fails to register with lay intellectuals. Their picture is of aircraft workers gaining and textile workers losing, and the idea that it is useful even for the sake of argument to imagine that workers can move from one industry to the other is foreign to them. Second, the link between productivity and wages is thoroughly misunderstood. Non-economists typically think that wages should reflect productivity at the level of the individual company. So if Xerox manages to increase its productivity 20 percent, it should raise the wages it pays by the same amount; if overall manufacturing productivity has risen 30 percent, the real wages of manufacturing workers should have risen 30 percent, even if service productivity has been stagnant; if this doesn't happen, it is a sign that something has gone wrong. (...) Associated with this problem is the misunderstanding of what international trade should do to wage rates. It is a fact that some Bangladeshi apparel factories manage to achieve labor productivity close to half those of comparable installations in the United States, although overall Bangladeshi manufacturing productivity is probably only about 5 percent of the US level. Non-economists find it extremely disturbing and puzzling that wages in those productive factories are only 10 percent of US standards.
Finally, and most importantly, it is not obvious to non-economists that wages are endogenous. Someone like Goldsmith looks at Vietnam and asks, "what would happen if people who work for such low wages manage to achieve Western productivity?" The economist's answer is, "if they achieve Western productivity, they will be paid Western wages" -- as has in fact happened in Japan. But to the non-economist this conclusion is neither natural nor plausible. (And he is likely to offer those Bangladeshi factories as a counterexample, missing the distinction between factory-level and national-level productivity).
- Constant employment is a reasonable approximation: The standard textbook version of the Ricardian model assumes full employment in both countries. But in reality unemployment is constantly a concern of economic policy -- so why is this the usual assumption? There are two answers. One -- the answer that Ricardo would have given -- is that international trade is a long-run issue, and that in the long run the economy has a natural self-correcting tendency to return to full employment. The other, more modern answer is that countries have central banks, which try to stabilize employment around the NAIRU; so that it makes sense to think of the Federal Reserve and its counterparts acting in the background to hold employment constant. This is not at all the way that non-economists think about the issue. Both supporters and opponents of free trade normally claim that their preferred policies will create jobs; free-traders are forever warning that the Smoot-Hawley tariff caused the Great Depression. And the alternative view does not come at all naturally. During the NAFTA debates I shared a podium with an experienced, highly regarded U.S. trade negotiator, a strong NAFTA suppporter. At one point a member of the audience asked me what I thought the effect of NAFTA would be on the number of jobs in the United States; when I replied "none", based on the standard arguments, the trade official exploded in anger: "It's remarks like that which explain why people hate economists!"
- The balance of payments is not a problem: The standard textbook presentation of the Ricardian model assumes balanced trade -- indeed, it is usually a one-period model in which trade must be balanced. Yet the news is full of stories about the balance of payments, of complaints about trade surpluses and deficits. Why are these absent from the story?
Again, economists have good reasons for thinking that it is a good approximation to separate balance of payments from real international trade issues. In Ricardo's case, the essential ingredient was the argument by David Hume that trade imbalances are self-correcting: a surplus country will acquire specie, leading to rising prices that price its goods out of world markets, while a deficit country will correspondingly find its goods increasingly competitively priced. In the modern world, again, the channels involve less Invisible Hand and more government intervention: when monetary policies target the unemployment rate, exchange rates do the adjusting. Economists are also aware that even persistent trade imbalances are not necessarily a problem, and certainly that surpluses are not a sure sign of health or deficits one of weakness. Trade may be balanced in Chapter 2; but Chapter 13 explains that the trade balance is equal to the difference between savings and investment, and that a country may justifiably run persistent deficits if it is an attractive site for foreign investment.
Again, none of this is obvious to non-economists. The essential accounting identity, savings minus investment equals exports minus imports, is if anything a better-kept secret than the concept of comparative advantage. The debate over NAFTA was entirely phrased in terms of the apparent prospect that the United States would run a trade surplus with Mexico -- that was why the treaty was in our interests -- and the deficit that has actually materialized is universally regarded as a bad thing.
In sum, while the concept of comparative advantage may seem utterly simple to economists, in order to achieve that simplicity one must invoke a number of principles and useful simplifying assumptions that seem natural and reasonable only to someone familiar with economic analysis in general."