China's traditional trade structure is

The structure of export commodities refers to the proportion of tangible export commodities and intangible export commodities (services) in exports. As far as tangible goods are concerned, it refers to the proportion of goods of different categories, grades and colors (according to the standard international trade classification) in the whole export. With the development of science and technology, the world trade commodity structure is inclined to high technology, service and "green products". In just 20 years, China's export commodity structure has jumped to a new level, but we should be soberly aware that the existing problems in China's export commodity structure are revealed by comparing with the changes in the demand structure of the international market and with the export commodity structure of developed countries and newly industrialized countries. The changing trend of international market demand and the steady growth of China's export trade, therefore, only by recognizing the situation clearly and adjusting, optimizing and improving China's own export commodity structure in time can we continuously improve the international competitiveness of China's export industries and products and ensure the sustainable development of China's foreign trade exports.

International trade theory is an important part of international economics, and it is microeconomics under open conditions. International trade theory mainly studies the exchange of goods and services between countries, the reasons, results and related policies of international commodity exchange. The research scope of international trade theory also includes the international flow of production factors and the international transfer of technical knowledge. On the one hand, factors of production and technical knowledge, as a special commodity, have their own international market; on the other hand, they play an important role as factor inputs in the production of goods and services. International trade theory also studies the mutual influence of economic growth, technological change and trade, and dynamically analyzes the causes and results of international trade changes.

From the historical perspective of economic theory, the theory of international trade can be traced back to the mercantilist theory of1the end of the 5th century1the beginning of the 6th century. In the trade theory of Smith and Ricardo, labor is the only factor of production, production technology is a given exogenous variable, and the rate of return on production scale remains unchanged. The trade theory of Smith and Ricardo is a part of the theoretical system of classical economics, which is called "classical trade theory". At the beginning of the 20th century, Swedish economists Herschel and Olin put forward the trade theory of "resource allocation" or "resource endowment". In the model of Herschel and Olin, labor is no longer the only input, but the scale reward of production remains the same. Their theory is called "neoclassical trade theory".

At the end of 1970s, with the rapid development and structural changes of international trade, the theory of international trade, which lingered in the Huxley-Olin system for many years, became active again. Some economists began to study the causes and results of trade in new ways, studied the new trade structure and trade policy, and created a series of new theories. After more than ten years of development, these theories have gradually matured. Some have been compiled into teaching materials, and some are still under discussion, which are still the frontier topics of trade. This paper will briefly introduce the new development of these trade theories and explain their significance to China's trade policy.

1. economies of scale, imperfect competition and trade between industrialized countries and the same industries.

The new explanation of the reasons for trade is mainly the "Theory of Scale Economy and Trade" developed from the late 1970s, and the main contributor is American economist paul krugman. This theory is based on the scale economy of enterprise production and the imperfect competition in the world market to explain the trade between the rapidly developing industrial countries after the war and between the same industries.

The development of the trade theory of economies of scale [( 1) A] is based on two assumptions different from previous theories: (1) The production of enterprises has economies of scale; (2) Incomplete competition in the international market.

Specifically, under the conditions of "scale economy" and "monopoly competition", the long-term average cost of enterprises decreases with the increase of output, and enterprises are faced with a market demand curve, and the market demand will increase with the decrease of prices. Before participating in international trade, enterprises only face domestic demand. Due to the limited domestic market demand, enterprises can't produce too much, so the production cost and product price have to be kept at a high level.

Enterprises participate in international trade, facing the expansion of the market, domestic demand and external demand to increase production. As the production is in the stage of economies of scale, the increase of output will reduce the average cost of products, thus increasing the competitiveness in the international market.

Because of the diversity of industrial products, it is impossible for any country to cover all the products of an industry, thus making international division of labor and trade inevitable. However, there is no fixed model for which country concentrates on which products can be produced naturally (competitive production) or by agreement. However, the basis of this "two-way trade" of industrial products between developed countries is economies of scale, rather than comparative advantages arising from different technologies or different resource allocation.

Two. International Trade, Technology Spillover and Economic Growth

Since the late 1980s and early 1990s, the research of international trade theory has mainly focused on the relationship among international trade, technological progress and economic growth. In the economic literature, although many theories have expounded the role of technology in trade and economic growth, the latest series of studies regard technology as an endogenous variable, which not only discusses the influence of technology on trade, but also analyzes the role of international trade and economic growth in technological progress. Combining technological change, imperfect competition, economies of scale and economic growth is the latest development and frontier subject of international trade theory.

The background of this new development of international trade theory is also related to the change of international trade pattern after the war. After explaining the reasons for the current "North-North trade" and the trade between similar products with the theory of scale economy and imperfect competition, people will naturally discuss it further. Why are there economies of scale? How are economies of scale and international division of labor formed? If the difference and development of technology is one of the important reasons, how does technology come into being, develop and spread? What is the relationship between the development of technology, international trade and economic growth? These problems have aroused great interest of international economists. Scholars combine international trade theory with growth theory and put forward many new viewpoints.

In recent years, in the research of international economics, there are many articles about international trade, technological change and economic growth. From its theoretical origin, it can be divided into two parts. Part of it, following Ricardo's model, still regards technology as an exogenous variable, but analyzes the influence of technological changes on trade patterns and welfare levels of countries from a dynamic perspective. The other part regards technology as an endogenous variable, which not only studies how technology affects trade and growth, but also studies the relationship between technological change, international trade and economic growth as the result of scientific research, investment, trade and economic growth.

1. Trade and growth theory with technology as exogenous variable

(1) Trade patterns formed by technological differences

In addition to the trade theory of "economies of scale and imperfect competition", technological differences are also used as exogenous variables to explain the trade of similar products between developed industrial countries. Markussen and Svencen (1985) assume in their research that the proportion of resource allocation and demand preference of the two countries are the same. Product production needs more than two elements, but it does not have economies of scale. But if there are some subtle differences in production technology between the two countries, the labor productivity will be slightly different. In the trade between the two countries, each country will export products with relatively high factor productivity.

Davis also assumed two industries in two countries in the study of 1994. Among them, the primary industry only produces one product, and the secondary industry produces two products that cannot be completely replaced. Suppose that one country is slightly different from foreign countries in the production of the secondary industry, and slightly superior to other countries in the production technology of one product. Under the condition of free trade, the equality of factor prices will make this country produce and export this product, while other countries produce and export another product.

The research of Markussen, Svencen and Davies shows that even in the market with constant scale returns and perfect competition, technological differences may lead to intra-industry trade between products in the same industry.

(2) The impact of technological changes on trade patterns and welfare.

Krugman studied the impact of technological progress on the welfare of developed and developing countries in 1986. In his model, he assumes that there are two types of countries: countries with advanced technology (developed countries) and countries with relatively backward technology (developing countries), and products are also divided into technology-intensive products and non-technology-intensive products. These assumptions are somewhat similar to the Heckschel-Olin model. Its development lies in: If technology changes (for whatever reason), what impact will it have on the trade patterns and welfare of countries?

If this technological progress occurs in developed countries, the result is harmless. First, for developed countries, its technology is higher and its products are more advanced. Because of its advanced technology, the production of updated technology does not face any competition and will not threaten other countries, so technological progress is good for it. Second, there is no harm to backward countries, because the technological gap has widened, giving them more room to develop and catch up. Therefore, the technological progress of advanced countries is beneficial to both types of countries. The only disadvantage for advanced countries is that for some products that already have technological advantages, technological progress and the improvement of production and export capacity may make the prices of these products fall and the terms of trade may become unfavorable.

What if technological progress occurs in backward countries? Krugman believes that the result is to narrow the gap between the two types of countries, which is a kind of competition for the original advanced countries and is not good for them. Backward countries will reduce their imports because they have the ability to produce this product, which will lead to two results: one is to reduce the price of this product, which is not good for advanced countries, and the other is to make intensive use of the scarce resources of backward countries if this product needs to be used.

2. Trade and growth theory with technology as endogenous variable.

On the other hand, the development of trade theory is to analyze technology as an endogenous variable, study the causes of technological changes, and also study the impact of technological progress on trade patterns and social welfare as the result of production and trade. There are two sources of technological change. One is passive, not developed through special research, but learned from fancy and doing. It comes through economic behavior, which is called "learning by doing". The technology mentioned here is not only production technology, but also management knowledge. The other is active and self-created. This technological change is an innovation. Technological innovation is usually the result of research and development (R&D).

(1) "Overflow" and "Learning by Doing"

The so-called technological change or progress is not always an unprecedented new invention. Many times, the so-called technological progress is just learning the advanced technology owned by others. This learning process is sometimes not the original purpose, but a natural by-product when engaged in production or other economic activities. As the owners of advanced technology, sometimes they do not intentionally transfer or spread their technology, but naturally export their technology in trade or other economic activities, which is called "technology spillover". No matter what technology, there is an overflow process. Most of the technological progress of "learning by doing" is obtained from technology spillover. Technology spillovers can be divided into international spillovers, domestic spillovers, inter-industry spillovers and intra-industry spillovers.

A) international technology spillover

International technology spillover refers to the direct or indirect diffusion of technology to other countries (such as through trade), so that producers in other countries gradually master these technologies.

In order to illustrate the international spillover of technology, we assume that there are two countries: country A and country B, and each country produces X and Y products respectively. When there is no trade between the two countries, the production of each country is determined by its own production technology and resource allocation. A country has a comparative advantage in producing X and B country has a comparative advantage in producing Y. If there is trade between the two countries, according to the theory of "comparative advantage", A country will specialize in producing and exporting X and B country will specialize in producing and exporting product Y ... This is the initial equilibrium after the transaction.

Now let's further assume that technology cannot be monopolized and can "overflow" to other countries through commodity trade. As a result of trade, producers in country AB have mastered each other's production technology and may adjust their own production. This kind of international technology spillover will produce various results. In one case, country A originally had a comparative advantage in producing commodity X, but country B has a more advanced technology and absolute advantage in producing X. Country A introduced the technology of country B to produce commodity X, which improved the productivity with comparative advantage. This result gives full play to the comparative advantage of domestic resources, which is conducive to the long-term growth of country A. In addition, commodity X was originally in short supply in country B, and it is no longer produced after the division of labor and trade between the two countries. Producing more X in country A can reduce the import price of country B, which is also beneficial to country B. The spillover of this technology has turned the trade pattern originally determined by "comparative advantage" into "absolute advantage". Both countries have benefited from technology spillovers.

However, if the technology of producing commodity Y in country B is more advanced than that in country A, country A will learn this technology from country B and use it to improve and develop the commodity Y that it does not have a comparative advantage. For country A, the result of this technology introduction is an import substitution growth, but for country B, it is a threat and competition. If the production of country A needs intensive use of its scarce resources, it may not be conducive to the long-term development of country A. Trade and technology spillover may lead the development in the "wrong" direction, thus affecting the long-term development speed of the two countries (see Yanagawa, 1993).

B) domestic technology spillover

Domestic technology spillover refers to the spread of technology in China. Due to geography, language, culture and other reasons, domestic technology spillover is faster than learning foreign technology.

In the late 1980s, Krugman and Lucas discussed the domestic technology spillover respectively. In Krugman's model (1987), he assumed that there were two countries, A and B, producing a series of products. Any one of them will have a preliminary leading position in the production technology of some products. Although technology can spread internationally, technology spillover will be faster in China. With the passage of time and the rapid process of domestic technology spillover, the country's once leading industries will have the possibility of accelerating development, and the original comparative advantages will be enhanced. "Domestic technology spillover" will also make other countries in a leading position in products with original comparative advantages, and the diffusion of technology in China will expand the differences among countries.

Lucas' model (1988) is somewhat similar to Krugman's, except that he assumes that a series of countries produce two products: X and Y. The labor force and labor productivity of different countries are the same, but the initial mastery of the technical knowledge of the two products is different. Some countries produce X, while others produce Y, forming the initial international division of labor. Due to the technology spillover from China, the countries that produce X and Y will continuously improve their labor productivity in their respective professional production, which makes the gap between countries in mastering the technical knowledge of the two products become wider and wider. Under normal circumstances, it is difficult to change the position of countries in the international division of labor, unless the growth rate of product labor productivity can't keep up with the decline rate of product prices, change the original position of international division of labor, and transfer the production of one product to the production of another product, which can only be those marginal countries.

The analysis of Krugman and Lucas shows that a country's initial comparative advantage, industrial choice and position in the international division of labor may be related to its own technical knowledge and resource allocation, or it may be due to accidental factors. However, once the initial industrial structure is formed, the spillover of domestic production technology makes a country's productivity in these industries increase faster than other countries, which will further consolidate its leading position in these industries. In a sense, this explains why some countries are good at certain industries, while others are good at other industries, which is related to domestic technology spillover. Moreover, once a certain production mode is formed, it is not easy to change, because industrial scale and domestic technology spillover will continuously improve labor productivity, and as long as the cost growth rate is lower than the labor productivity growth rate, it will be profitable and continue to exist. History plays an important role in determining a country's long-term production and trade pattern.

C) technology spillovers between industries and within industries

Technology spillover may also occur between different industries and within industries. Although the products of many industries are different, many of the resources used are the same. How to improve factor productivity can promote all industries. In addition, the concept of "technology" here is not limited to specific production methods, but also includes technical knowledge in management. Therefore, the technological advantages of one industry may also spill over to other industries, which will also improve the productivity of other industries and have an impact on the long-term development of society. 〔 1)c〕

There may be different industrial clusters in the same industry, and the products produced by each group are similar but the production technology will not be exactly the same. Compared with similar foreign industrial groups, it will also have different advantages in production. International trade and the resulting competition and technology spillover will shorten the technology gap between industrial groups.

(2) Development research (R&D) and technological innovation (innovation)

Another source of technological change is technological innovation, which is the result of investment, development and research. The development of new technologies is mainly manifested in: a) improving factor productivity, producing more products with limited resources, or using less resources while ensuring output; B) product quality improvement and new product development.

Technological innovation or developmental technological progress can appear in the improvement of specialization. With the socialization of production and the refinement of division of labor, a final product can be produced by one enterprise to many enterprises. The same enterprise can also be divided into many departments, and each department only produces a part of products. The improvement of specialization makes all departments focus on small-scale mass production, and in this specific component production, enterprises may make profits by reducing costs. In other words, with the improvement of specialization, profits are no longer just obtained from the final products, and all production links are independent, so there is the possibility of profit. The pursuit of profit makes every link of production have the motivation to improve technology.

Development-oriented technological progress is often obtained in the development of new products. Market competition forces enterprises to continuously develop new products or improve product quality, thus generating new technologies.

Different from "learning by doing", technological innovation or developmental technological progress requires a lot of investment and research. Therefore, only when these investments can be profitable will enterprises develop new technologies. Therefore, whether a country can achieve substantial development-oriented technological progress requires two necessary conditions: (1) intellectual property protection, because without protection, the risks taken by enterprises in developing new products are asymmetric with their benefits, and there is no incentive for investment and research. (2) Encourage investment in scientific research. Although learning by doing can also improve technology, it has its limitations. After all, only advanced technology can shorten the gap. If a country wants to be technologically advanced, it must have developmental technological progress, but it needs the protection of law and investment.

There is a mutually reinforcing relationship between international trade and development-oriented technological change. The influence of trade on technological innovation not only forces countries to develop new technologies and products through international market competition, but also gives countries the opportunity to inspire each other through international technology spillover. The development of new technologies is no longer just the behavior of a single country, but the joint efforts of all countries. There are still problems of economies of scale in technological development. In a sense, the international flow of trade and technology can make R&D form "economies of scale" and reduce the cost of R&D in various countries. After a new technology is started in one country, another country can immediately introduce it and further develop it on this basis, instead of repeating the same process. Of course, this requires many political and technical conditions, but from an economic point of view, this is an optimal way to allocate resources.

On the other hand, technological innovation will also affect the trade pattern. In the model of technology as exogenous variable and "learning by doing", the initial trade model is given, and it is assumed that there is a gap in production technology among countries, but why there is a gap is not discussed. The model of technology as an endogenous variable reveals the root of the technology gap. Throughout history, we can see that although the process of technology spillover and learning by doing at home and abroad may shorten the technology gap between countries, China's original resources and technical conditions still play an extremely important role in a country's long-term development and position in the international division of labor. Therefore, strengthening investment in development research and constantly developing new technologies are necessary measures to improve a country's trade position and ensure long-term economic growth.

Three, the new theory of international trade for China's further reform and opening up.

In the past fifteen years, although we have made great achievements in opening up, our trade policy is still bound by many traditional concepts. We have made a lot of efforts in export, but we are worried about opening up the domestic market. In the process of applying for restoring the status of GATT, we regard expanding imports and opening up the market as a price for entering GATT, an "obligation" that we have to bear in order to obtain certain rights, and its idea comes from the theory of "protecting infant industries" to a great extent.

China is still a developing country, so it is necessary and understandable to protect certain industries. The question is, how to choose the object of protection? How to protect it? What are the prospects and costs of protection? We must fully estimate the cost of protection and strive to achieve our goal of developing advanced or immature industries at the lowest cost.

Classical and neoclassical trade theories analyze the losses caused by protection to consumers and the welfare of the whole country. The theory of technology spillover and learning by doing reveals the "external effect" lost in protection, especially the restrictions on the import of high-tech products such as computers, which not only lose the interests of consumers, but also delay the process of technology spillover and learning by doing. Scientific and technological knowledge products such as computers are different from general consumer goods. The use and popularization of computers include the popularization of science and technology and the improvement of labor productivity. The external effects brought about by the rapid popularization of computers cannot be measured by money. Moreover, the key to the development of computer industry is not hardware, but software. Only on the basis of popularization can there be enough human capital and market demand to promote the development of software. We must consider the costs and consequences of protecting infant industries through trade barriers.

The trade theory of scale economy also puts forward many new ideas for China's trade policy. The new trade theory reveals the characteristics of monopoly competition and trade in manufactured goods in the contemporary international market. The diversity of industrial products makes it impossible for any country to have enough resources to produce and export all industrial products. There is more and more room for international trade. Even in the same industry, there may be both imports and exports. Modern international competition is not limited to the gains and losses of individual products. Therefore, there is no need for us to restrict the import of foreign high-quality products, and there is no need to produce products that are already dominant abroad through protection. Opening some markets to the outside world does not mean that similar industries in China cannot develop. If someone else produces a certain model, we can concentrate our resources on producing other or new models and reduce the cost of exporting abroad through economies of scale.

How to make some industries form economies of scale? The theory of scale economy and trade puts forward a problem of "strategic trade protection". Due to the imperfect competition in the international market and the existence of modern enterprise scale economy, how to expand the international market share to expand production and reduce costs has become the key factor for enterprises to win in international competition. If the government can correctly select some promising industries and give full play to their resource advantages, and help them reach a certain production scale through policy support, it will be beneficial to their own interests and development. This kind of trade protection focuses on a country's long-term strategic development and is called "strategic trade protection".

Many countries have adopted strategic trade protection policies, such as Japan, which also protected many industries during the post-war economic development. It protects an industry for a period of time and then transfers it. The purpose of protection is only to make the industry produce a kind of technology spillover and self-expansion ability during the protection period, and improve labor productivity and competitiveness in a short time. The protection time is short, and the protection industry is constantly changing. Krugman borrowed from givens (1982) and called it "narrow moving belt".

Whether it is a free trade policy or a "strategic trade protection" policy, the choice is based on how to maximize national interests. This benefit should be not only estimated statically, but also considered dynamically. For any industry and any policy, we should analyze the advantages and disadvantages as accurately as possible. The new international trade theory does not tell us whether we should protect it, but provides more problems for our trade policy choice. Simply using trade barriers to protect infant industries is a passive and outdated way, and the cost is not small. From the perspective of strategic development, protecting certain products (not necessarily the whole industry) may bring long-term advantages and benefits, but these products are not necessarily infant industries, and the means of protection are not necessarily trade barriers, but industrial policies or consumption policies with lower costs. The protection period should be short, which is positive and promising.