采纳比较优势的利弊

RESEARCH SEMINAR IN INTERNATIONAL ECONOMICS School of Public Policy The University of Michigan Ann Arbor, Michigan 48109-1220 Discussion Paper No. 423 Benefits and Costs of Following Comparative Advantage Alan V. Deardorff University of Michigan January 12, 1998 Recent RSIE Discussion Papers are available on the World Wide Web at: http://www.spp.umich.edu/rsie/workingpapers/wp.html 2 Benefits and Costs of Following Comparative Advantage Alan V. Deardorff The University of Michigan The Sweetland Inaugural Lecture, Presented at the 45th Annual Conference on the Economic Outlook, Ann Arbor, Michigan November 20, 1997 January 12, 1998 Paper: bcca.doc ABSTRACT Benefits and Costs of Following Comparative Advantage Alan V. Deardorff The University of Michigan This paper is the text of a lecture given on November 20, 1997 to inaugurate the John W. Sweetland Chair in International Economics, in the Department of Economics of the University of Michigan. Its message is that international trade theory, and in particular the theory of comparative advantage, is really just an application of benefit-cost analysis. This is true both of many of the tools of trade theory, which are familiar as the same tools by which benefit-cost examines all sorts of public projects and policies, and of the implications of the theory. Trade theory does not say, as sometimes claimed, that international trade is necessarily and always good for everyone. On the contrary, the theory of comparative advantage identifies both winners and losers from international trade, and the subtlety of the argument, much like many applications of benefit-cost analysis, consists of quantifying and comparing the gains and losses. The paper works through both the partial and the general equilibrium analyses of trade under a range of assumptions from implausibly perfect to realistically messy. It discusses who gains and who loses from trade in each case, as well as the strength of the argument that the gains outweigh the losses. Keywords: Comparative Advantage Correspondence: Gains from Trade Alan V. Deardorff JEL Subject Code: F1 Trade Department of Economics University of Michigan Ann Arbor, MI 48109-1220 Fax. 313-763-9181 E-mail: alandear@umich.ed http://www.econ.lsa.umich.edu/~alandear/ January 12, 1998 Benefits and Costs of Following Comparative Advantage Alan V. Deardorff The University of Michigan I. Introduction Let me start by thanking several people who have helped to make this event possible. First and foremost is of course John Sweetland, whose gift to the university funded the Sweetland Chair. John has been a most extraordinary friend to the department and a benefactor far beyond anything we could have hoped for. His gift of this chair, and his promise of several more together with additional funds for graduate student support, will I hope be decisive in helping us to strengthen the ranks of our faculty and students. Also of course, I personally owe him a debt of thanks in exchange for the financial benefits that accompany the chair. And I want to thank him for not vetoing me as the holder of the chair, knowing as he does how ignorant I am about international trade in cement. In addition, I would like to thank Saul Hymans for the important role he played in facilitating John’s decision to help the Department and for inviting me to give this lecture here at the Outlook Conference. I am especially grateful to my colleagues in the Department of Economics for awarding me the chair, especially Paul Courant who was Department Chair when the decision was made. I feel extremely honored. I owe thanks also to several colleagues and students with whom I have discussed the topic of this 5 lecture, especially Bob Stern, Jim Levinsohn, Saul Hymans, and two of my students, Ting Gao and Simeon Djankov. Finally, let me thank my family, three of whom are here this evening. I thank my wife, Pat, for putting up with my distracted frame of mind for the last few days as I’ve tried to think of what to say, and I thank my kids, Ryan and Allie, for putting up with it as well, although we see so little of each other these days that I doubt they noticed. Most of all, I thank them all for coming this evening to listen. I know that neither economics nor international trade are high on their list of interests. My topic tonight grows out of 27 years of teaching comparative advantage and out of less than one year of teaching benefit-cost analysis. Two years ago, the dean of the School of Public Policy, then Ned Gramlich1, asked me if I would teach benefit cost. I felt that I knew nothing about the subject, but he assured me that I did. “That’s all trade theory is,” he said. And he was right. As you will see tonight, I had been “speaking benefit cost” my whole career, without knowing it. Another reason for talking about this tonight is a certain amount of irritation I have felt with the public’s lack of understanding about what economists know about comparative advantage. I don’t mean the difficulty they have in understanding the concept of comparative advantage itself. That is a tough one, which my colleagues and even I get wrong from time to time when we’re not careful. No, what bothers me is two opposite misperceptions that many in the public seem to hold at once. One is that the 1 Who is now a Governor of the Federal Reserve System. It’s hard to believe that this really nice guy, with whom several of us have played low-stakes poker here in Ann Arbor, is now playing in the biggest poker game there is. With our money! 6 theory of comparative advantage is only valid under very limited and special circumstances. The other is that economists believe it to be valid under all circumstances. Neither is true. On the one hand, the theory of comparative advantage is much more broadly valid than you would guess from the simple numerical examples that may have been your only exposure to it. But on the other hand, there are limitations to the theory, and we economists are very well aware of them. Before I try to make this clearer, let me first remind you of what comparative advantage is. A simple definition is this: Comparative advantage is low relative cost of a good compared to other countries. This statement may appear to be repetitive, using the two words “relative” and “compared to” redundantly. Doesn’t “relative” already mean that something is being compared? Yes, but in this case it is being compared to something else. “Relative cost” here means the cost of a good relative to other goods. It is then this price ratio that is to be compared across countries. Comparative advantage, then, involves a double comparison, across both goods and countries, and that is critical both to understanding it and to why it works. Because it is such a double comparison, for example, it is impossible by definition for a country to have a comparative disadvantage in every good. The worst that could happen would be that all of these ratios of costs be the same across countries, in which case the countries would have neither comparative advantage nor comparative disadvantage in anything. That would require an incredible coincidence. In practice, every country will have a comparative advantage in something. So far this is just a definition. The importance of the concept of comparative advantage is the economic theory that incorporates it and that generates what has been called the Law of Comparative Advantage. Actually, there are two laws, one “positive” 7 predicting what countries will do if given the chance, and one “normative” implying what countries should do: The Positive Law of Comparative Advantage: If permitted to trade, a country will export the goods in which it has a comparative advantage. The Normative Law of Comparative Advantage: If permitted to trade, a country will gain; i.e., the benefits of trade exceed the costs. Both of these points are routinely made in the most elementary introductory economics courses, but they are illustrated using a numerical example much like David Ricardo used 200 years ago to explain comparative advantage when he discovered the idea. The example has just two countries and two goods, both of which are used only for consumption, only one factor of production (homogeneous labor), perfect competition, and perfectly free trade without even transport costs. The example is so unrealistic that perhaps students can be forgiven for thinking that it has little bearing on the world they live in. But in fact, both of the laws of comparative advantage have been shown to be valid in much more general models, dropping every one of these assumptions. That is one of the messages that I want to get out, the good news that I want to spread: Comparative advantage and its implications are much more robust than even many economists are aware, if they do not specialize in trade. The fact that the real world is incredibly complicated, with all sorts of goods and services being produced in all sorts of ways and used for all sorts of purposes, with all sorts of natural and artificial barriers to international trade, does not undermine the economic basis for trade following the pattern of comparative advantage and thereby being beneficial. 8 On the other hand, even these broad generalizations of the laws of comparative advantage still do require some assumptions, assumptions that are frequently violated in practice. Furthermore, even when those assumptions are not violated, notice that the normative law does not say that everybody gains from trade. It acknowledges that there are costs due to trade, and then says that there are also benefits that are larger. For both of these reasons, then, there is a downside to international trade of which economists are well aware. Indeed, no responsible economist will teach that trade is an unambiguously good thing. Even in the best of worlds, some people lose from trade, and the case for free trade is only that other people gain more. Furthermore, this is not the best of worlds, and there are many conditions in the real world that may, in some cases, cause even the net effects of trade to be harmful. We know this, but the tools of comparative advantage and trade theory also tell us many things about how best to deal with these conditions. The bottom line, at least for the many quantifiable benefits and costs due to trade, is that once one accounts for all of them, in most cases we are better off not restricting trade. Rather we should permit it to occur freely, following comparative advantage. There are other more appropriate means of dealing with the failings of the economy than restricting trade. In other words, the case for liberal trade is neither weak nor simple. It requires a careful and dispassionate look at all of the benefits and costs of trade. That is what I will attempt in the rest of this lecture. II. A Standard Benefit Cost Analysis of Opening a Single Market As I have learned in this last year of teaching, the standard tools of benefit cost analysis are simply supply and demand. Most benefit cost studies focus on individual markets and 9 use the tools of partial equilibrium analysis to identify and quantify benefits and costs within those markets. These tools are easily applied to international trade. I will not attempt to actually do such an analysis here – we’ve just had dinner, after all. But I cannot resist showing you these tools for you to admire. Figure 1 shows two supply and demand diagrams, panel (a) for an export and panel (b) for an import. The lessons that could be derived from these diagrams if we had the time and inclination are summarized in Table 1, as follows. The direction of trade – whether a good is exported or imported – depends simply on whether its domestic price is above or below its world price. If it is below the world price, then the good will be exported. This will benefit the suppliers of the good, both the owners of the firms that produce it and the workers they employ. But it will harm domestic demanders of the good who will be forced to pay more for it, and these demanders include not only consumers, if it is a final good, but also other producers (and their workers) who use the good as an input. What the theory shows, however, is that the gains on the supply side of such a market are larger than the losses on the demand side, in the sense that the gainers could afford to compensate the losers and still remain better off. The net gain from exports, if you are interested, is the shaded triangle in Figure 1(a). If the domestic price of a good is higher than the world price, then the direction of trade will be the opposite: it will be imported. Here again their are gainers and losers, but they are on opposite sides of the market from the other case. It is the demanders of imports who gain from their lower price, again both consumers and firms buying them as inputs. And it is the suppliers, not of the imports themselves but of domestic goods that compete with them, who lose. It is this cost to import-competing suppliers, both firms 10 and workers, that is often the most visible effect of trade. The losers themselves as well as advocates on their behalf often seem to believe that economists are simply unaware of this cost, but we are not. Our models, as you see here, include that loss and trust me, we do take it seriously. But we do not focus on it exclusively, as the suppliers themselves may understandably want to do. We must look at the benefits as well as at the costs. Now you might think that, since everything else in the import case is opposite to what it was in the export case, the net welfare effect should be negative. But lo and behold, it is not. The net effect is positive, as shown again by the shaded triangle in Figure 1(b). Need I say more? Take it as part of the miracle of comparative advantage that, when trade follows the dictates of comparative relative prices (for that is really what is happening in Figure 1), the gains outweigh the costs in markets for both exports and imports. Or, if you want more of a reason for this result, note that as prices move away from domestic market equilibrium toward their world levels, the losers in both markets cut their losses, reducing their quantities bought or sold, while the gainers take advantage of the opportunity by increasing quantities. It is these induced changes in quantities that generate the net gain in both markets. The bottom line in Table 1 then, literally, is that a standard benefit cost analysis of international trade yields an unambiguous result: benefits are greater than costs. III. General Equilibrium Analysis of Opening a Whole Economy From the time of Ricardo, trade economists have recognized that there is more to trade than can be captured in a partial equilibrium analysis like Figure 1. Trade affects so much of the economy simultaneously that its full effects must include numerous 11 interactions among different markets. Most importantly, partial equilibrium analysis cannot capture the effects of trade on factor markets, especially on wages, which turn out to be both important and often contentious. Trade theorists have developed a variety of distinctive tools to analyze the general equilibrium effects of trade, and they have used these tools to establish several important results that concern us here. As before, there is no real need for you to see the tools themselves, but I cannot resist showing you some of them. Figure 2 includes two of the most distinctive general equilibrium diagrams from trade theory, panel (a) illustrating the gains from trade and panel (b) illustrating how one factor of production – in this case labor – may lose from trade due to a drop in its real wage. More important are the results themselves, which are summarized in Table 2. In addition to all of the effects on suppliers and demanders from Table 1, which still tend to be true on average for most markets even in general equilibrium, Table 2 reports effects on factors of production. It turns out that these effects depend on several different aspects of a factor’s relationship to industries and to the economy. Factors of production that are “specific” to an industry, for example, in the sense that they cannot leave it but are also not subjected to competition from entry by more of the same factor, gain or lose from trade depending upon whether their industry exports or imports. But factors that are mobile among industries do not depend directly on the performance of the industry in which they are employed, but rather on how trade overall affects their economy-wide factor market. For example, owners of a factor that is used intensively in export sectors will gain from trade, even if the particular units of the factor that they own are employed elsewhere. Likewise, owners of factors that are abundant in the country compared to 12 other countries will also gain, as trade provides an outlet for what they can produce. But the flip side is that owners of scarce factors, and of factors used intensively in import sectors, will lose in real terms from trade. This is the famous Stolper-Samuelson Theorem, proved over fifty years ago by Paul Samuelson, who later won the Nobel Prize, and Wolfgang Stolper, who has spent most of his career on our own faculty. This theorem, which identifies both gainers and losers from trade within a country, has become more important with time as international trade has grown. Applied to the United States, with our abundance of skilled labor and scarcity of unskilled labor, the Stolper-Samuelson theorem implies that trade will make low-wage unskilled workers worse off. This indeed has been happening over the last 15 or 20 years, and while there are other contributing causes of this phenomenon as well, there is little doubt but that the opening of world markets and the growing competition from low-wage labor abroad have played a role in the rising inequality among American workers. The general equilibrium models of trade theory also establish, however, that whatever some factor owners may lose from trade, other factor owners must gain even more. Once again, the benefits of trade outweigh the costs, as stated in the bottom line of Table 2. This is important, for it means that it should be possible to devise social policies that offset the harm to low wage workers while leaving the overall gains from trade to be enjoyed by all. Whether our existing policies accomplish this, however, is another matter. 13 IV. The Role of Distortions All of the results discussed so far arise under a large number of assumptions. These assumptions do not require, as I noted above, any limits on the numbers or kinds of goods, factors, or countries. Nor do they require free trade. But most of them do require perfect competition (i.e. that market participants are all too small to be able to influence prices) as well as that markets clear (supply equals demand), that producers and consumers bear and enjoy the full costs and benefits of their actions (no externalities), and that buyers and sellers face the same prices (no taxes or other government intervention). All of these assumptions are needed for markets to work as well as possible, and because international trade is just the working of markets on a grand scale, these assumptions are also needed for proofs that the benefits of trade outweigh its costs. Economists follow the endearing practice of calling any failure of these assumptions a “distortion,” as though it is somehow the economy’s fault th