1. Productivity and exports
Melitz(2003) proposed a heterogeneous enterprise trade model to explain the differences between enterprises and export decision-making behaviors in international trade. The dynamic industrial model of heterogeneous enterprises established by Melitz is based on Hopenhayn( 1992) general equilibrium framework, which extends Krugman( 1980) trade model and introduces the difference of enterprise productivity.
The research results of Melitz(2003) show that trade can induce enterprises with higher productivity to enter the export market, while enterprises with lower productivity can only continue to produce for the local market or even withdraw from the market. International trade further redistributes resources and flows to more productive enterprises. Due to the redistribution of resources, the overall productivity of the industry has been improved. This kind of welfare is a trade gain that was not explained by previous trade theories. Enterprises with the highest productivity will be able to bear the fixed costs of overseas marketing and start exporting, while enterprises with medium productivity will continue to produce for the local market. When tariffs are reduced, transportation costs are reduced, or the scale of export market is increased, the productivity of the whole industry will increase accordingly, and these trade measures will increase the average productivity of local and export markets. Bernard, Eaton, Jensen and Kortum(2003) also established a heterogeneous enterprise trade model. Different from Melitz(2003) model, BEJK model adopts the market structure of Bertrand competition rather than monopoly competition, and mainly focuses on the relationship between enterprise productivity and export. Bernard et al. simulated a 5% reduction in global trade barriers, and the results showed that due to the closure of low-productivity enterprises and the expansion of exports by high-productivity enterprises, the trade volume increased by 39%, and the total productivity also increased. Melitz and Ottaviano(2005) studied the relationship among market size, productivity and trade, and pointed out that the competition intensity in different markets is determined by the number of enterprises in the market and the average productivity level, and market size and trade will affect the competition intensity and market decision-making of heterogeneous enterprises. The total productivity level depends on the dual role of market size and the degree of market integration brought about by trade. The higher the degree of market integration, the higher the level of productivity and the lower the profit. This model has certain reference value for studying the influence of regional trade integration.
Ye apple(2005) tries to explain the institutional differences between export enterprises and non-export enterprises. Yeaple linked the trade cost with the decision-making of enterprises in four aspects: entry, technology selection, whether to export or not, and the type of workers employed, which effectively explained the reasons for the increasing technology premium. The innovation of y eapple(2005) model is that firm heterogeneity is the result of the interaction of transaction costs, technical characteristics and workers' technical heterogeneity, which is also of great significance to the impact of international trade on technology premium and observable industrial productivity.
In 2007, Deng Xiang and Zheng Lu believed that the new new trade theory successfully introduced enterprise heterogeneity into the international trade model, and explained the occurrence and influence of trade from the micro level, thus opening up a new field of international trade research. This paper explains why good enterprises do international trade and poor enterprises do domestic trade. The theory holds that free trade can improve industrial productivity and social welfare, so free trade should be advocated rather than trade protection in policy.
In April 2009, Li and Wang Ling abandoned the assumption that the marginal cost of enterprise production is unknown and obeys random distribution, and introduced the assumption that the marginal production cost of technology and products is predictable in the literature of enterprise technology selection, which expanded and supplemented the existing model to a certain extent, and pointed out that enterprises should not be given export concessions and subsidies, but should create a good and fair market environment for their independent choice.
2. Exports and foreign direct investment
Helpman, meitz and y eapple(2004) extended the Melitz model and considered the decision of establishing overseas branches, that is, whether enterprises internationalize in the form of export or FDI. The research of Helpman, Melitz and Yeaple shows that the choice of export or foreign direct investment is decided in advance by the enterprise according to its productivity. From the empirical test, the adoption of deviation method improves the prediction ability of the model, which is helpful to better understand how the globalization strategy of enterprises and the change of export cost or FDI cost affect the production methods of various countries and industries. Helpman, Melitz and y eapple(2004) have made outstanding contributions to the study of the relationship between export and FDI, just as Melitz(2003) did to the study of trade among heterogeneous enterprises. After introducing the characteristics of enterprise heterogeneity, we can distinguish different enterprises in the same industry and determine which enterprises are engaged in export and which enterprises become multinational companies. The difference of enterprise productivity enables enterprises to choose independently. Only enterprises with the highest productivity will become multinational companies, enterprises with medium productivity will export, and enterprises with low productivity will only sell in the domestic market.
In 2009, Li expanded the theoretical model based on the new trade theoretical framework at the forefront of international trade, and concluded that enterprises with high productivity should choose foreign direct investment and enterprises with low productivity should choose export trade. At the same time, based on the 1997) data of 36 industries in China in 2006, this paper calculates and corrects the total factor productivity of industries in three different ways, applies the theory to practice, and analyzes the internationalization path choices that different industries in China should have.
In May 2009, Sun made a systematic and comprehensive comparison between neoclassical trade theory and new trade theory, analyzed the characteristics of new and new trade theory from two aspects: the basis of trade division and international trade income, discussed the practical significance of new and new trade theory to China's participation in international economic activities, and looked forward to the future research direction of new and new trade theory. It is pointed out that under the objective existence of enterprise heterogeneity, the state must effectively support its large enterprises and provide specific support variables to improve the trade income of open economy.