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欧盟FDI对中国贸易结构的影响研究

Studying on the Impact of EU’s Direct Investment on Chinese Trade Structure

【作者】 毕红毅

【导师】 范爱军;

【作者基本信息】 山东大学 , 国际贸易学, 2014, 博士

【摘要】 贸易和投资一直是当代国际贸易学领域的热点研究问题。1957年美国学者罗伯特·蒙代尔(Robert A. Mundell)首先提出投资和贸易替代理论,自此之后投资和贸易的关系被许多学者所重视,理论界除了对替代学说的补充发展,日本学者小岛清(K. Kojima,1981)提出的“边际产业扩张论”是互补关系学说方面最具代表性的理论,小岛清理论模式认为对外直接投资可以是创造贸易的,也可以是破坏贸易的。近年来还有学者提出投资和贸易的关系是不确定的理论,但这并不是研究的主流,也就是说目前理论界对贸易和投资的关系可以大致归结为投资替代贸易和投资创造贸易,但是这些学说研究的方向都是发达国家的投资对其本国贸易的替代和创造作用。自上世纪80年代中期以来,伴随着世界新兴工业化国家的出现和发展中国家的崛起,发达国家的对发展中国家的投资呈逐年增加的趋势,发展中国家已经逐步成为发达国家的主要投资接受地,尤其是中国利用外资所带来的经济的高速增长,引起国内外学者的普遍重视。学者们开始从多个角度研究投资的作用,出现了许多新的研究成果,我国学者做出了大量的研究,分别从理论和实证两个方面研究外商直接投资对我国经济和贸易的影响。但是这些研究主要集中在世界各国直接投资对我国贸易规模和贸易竞争力的影响,较少有学者研究直接投资对我国贸易结构的影响。本文研究领域主要是外商直接投资对我国贸易结构的影响,主要选取欧盟对华直接投资对我国贸易结构的影响做为研究对象。选取欧盟的原因是中国和欧盟都是世界经济舞台的主角。欧盟既是全球经济总量最大的经济体,也是由28个发达经济体组成的、迄今为止世界上最为成功的区域经济一体化组织。中国是世界经济发展最快最大的发展中经济体。2013年11月21日,国务院总理李克强在人民大会堂同欧洲理事会主席范龙佩、欧盟委员会主席巴罗佐共同主持第十六次中国欧盟领导人会晤时双方在共同制定的《中欧合作2020战略规划》①指出:中欧经贸关系是世界上规模最大、最具活力的经贸关系之一。双向贸易和投资成为促进中欧各自经济发展和创新的主要动力。中欧都肩负着继续拉动世界经济增长,实现共同繁荣的重要责任。双方致力于塑造发展创新、增长联动、利益融合的世界经济,坚定维护和发展开放型世界经济。为此,中欧决心本着互利的精神,进一步深化面向2020年的贸易与投资关系,促进开放、透明的市场和公平的竞争环境。特别重视为中小企业提供更多机会。②这也是本文研究的意义。与以往的研究相比,本文主要探索三个问题:一是外来直接投资对东道国的贸易结构会产生怎样的影响?二是中欧贸易结构有哪些互补性和差异性?三是欧盟对华直接投资对我国的贸易结构产生了什么影响?本文的创新也是围绕这三个问题进行的:一是探索构建外国直接投资与东道国进出口贸易结构变化的理论模型,并对贸易结构的影响机制进行理论分析,尝试对外国直接投资与东道国进出口贸易结构变化进行一般性的理论解释。二是运用统计学的研究方法,归纳整理欧盟十五国和新加入欧盟的新十一国(塞浦路斯找不到研究资料)对中国的投资和进出口结构状况进行全面的查找、归纳和整理,通过大量的分析对比,研究中欧贸易结构的互补性和差异性。三是运用所整理的研究资料、研究数据,运用所构建的理论模型进行实证检验。本文按照文献综述——双边研究现状对比研究——理论研究——实证研究的逻辑结构进行分析。第一大部分,对欧盟对华直接投资和中欧进出口商品结构进行了统计对比,分别测算了贸易商品贸易竞争力指数。本文采用国际贸易商品分类目录HS编码为分析依据,以OECD的产业分类为基础,将产业按技术层次的高低分为高技术产业、中高技术产业、中低技术产业、低技术产业,按照其所属的产业,分别挑取了中欧双边关联度大的四十四章的所有进出口货物作为研究对象,对这四大类44章商品所包含的所有商品种类至少二十年的进出口数据进行搜集,分析不同技术水平进出口产品的占比,比较客观、详实地分析我国同欧盟的进出口商品贸易结构的变化情况。对欧盟FDI同其他对华投资经济体进出口商品结构进行了统计对比;测算了我国与欧盟原十五国贸易商品贸易竞争力指数;测算了中国与欧盟新十一国贸易商品贸易竞争力指数。上述研究中发现:原欧盟十五国对华直接投资主要集中于制造业和化工橡胶和塑料制品、金属制品、机器和设备工业,电气等行业。欧盟国家在这些行业的设备投资和技术类中间产品的向我国的出口,是我国获取关键设备和先进技术的重要来源之一。欧盟对华投资企业多为资本密集型,单个项目投资金额较大,技术含量较高。2012年,欧盟对华直接投资的平均项目金额达360万美元,美国为228万美元,欧盟是美国的1.6倍;亚洲国家平均项目金额共481.33万美元。可见欧盟国家对华投资大多集中在一些高增长、对经济影响较大和产业关联度比较强的部门。在转让技术方面,欧资企业明显优于美国对华投资企业,更优于日资企业。欧盟的投资在增加我国国内资本的同时,能够通过技术转让、技术溢出等方式把先进的技术和管理经验带到我国,对我国进出口商品结构起到优化作用。就贸易而言2001年之后,中欧双边产品出口量均明显增长,中高技术水平产品增长速度最快,出口量也最大,其次是高技术产品,而低技术产品虽然也有迅猛增长,但是地位却已经逊于中高技术产品和高技术产品。在进口方面,我国从欧盟原十五国中进口的中高技术产品一直是四种类型中最多的,增长速度也是最快的,其次是高技术产品。因此,综合来看,我国从原欧盟十五国进口的产品中,中高技术和高技术产品占主要地位。其中机电设备是我国从欧盟十五国进口最多的商品,其次是航空航天类产品。无论从出口还是进口来看,我国与欧盟的贸易结构与其它对华投资的经济体相比都是最合理的。在与欧盟新十一国的贸易方面,我国对欧盟新十一国的产品出口额远远低于同欧盟原十五国的出口额,但是近年来也呈稳步上升趋势,未来还有很大发展空间。第二大部分,本文借鉴相关理论,研究了FDI对东道国出口商品结构的影响机理和FDI对东道国进口商品结构的影响机理。本文以Dornbush,Fischer and Samuelson(1980)的模型(简称DFS模型)为基础并作进一步扩展。本文构建的计量模型与DFS模型的主要区别是:在DFS模型的基础上,并分别讨论了外资对东道国出口商品结构的影响以及技术引进对东道国出口商品结构的影响,分析了引进外资对东道国进口商品结构可能产生的影响,最后比较了引进外资和引进技术对东道国出口结构影响的差异。因为第三章的统计研究显示出:欧盟对华直接投资的主要特点是直接投资带动了高新技术的输入,也就是说我国在引进欧盟直接投资的同时引进了大量的先进技术;尤其是欧盟原十五国对华直接投资主要是集中于我国的中高技术产业,投资倾向于资本技术密集型产业,因此本文在借鉴学者们研究的基础上,把直接投资和技术进步纳入理论模型进行变量分析,构建外国直接投资与东道国出口贸易结构变化和进口商品结构变化的理论模型。分析了在开放条件下外商直接投资对一国出口商品结构的一般性影响,分析了引进外资对本国要素结构、单位成本、比较优势及出口结构的影响,其基本结论是:本国引进外资后,劳动与资本的相对比例变小,劳动力相对工资上升,资本的使用成本(利率)下降,导致本国部分劳动密集型产品的优势在下降,于是本国缩减了这部分劳动密集型产品的生产规模,因此可以加大在资本密集型产品的投入,在部分资本密集型产品的生产上开始具有比较优势,这导致本国的优势产品既包括劳动密集型产品,又包括部分资本密集型产品,即本国的优势产品种类增加,同时外国的优势产品种类在减少。外国比较优势产品种类的减少会刺激投资国研发新的技术,投入到生产领域中,从而使投资国和东道国的产业结构都在不断优化。关于FDI对东道国进口商品结构的影响机理,本文认为外资进入东道国后,会对东道国进口商品结构也产生重要影响,这种影响可能比较复杂。在外资进入东道国初期,可能山于对东道国的产业政策以及产业技术水平并不十分了解,同时也为了防止核心技术的溢出,新进入企业往往从海外母公司进口核心零部件或技术含量较高的中间产品。这时东道国会因为外资的进入而增加了对中间产品的进口。经过一段时间之后,外资会加深对东道国的产业政策以及产业技术水平的了解,为了节约生产成本和更加适应东道国当地市场的需求,外资一般会选择在东道国当地研发、制造中间产品,这会减少东道国对外来中间产品的进口。因此,外资的进入对东道国进口商品结构的影响主要取决于中间产品在何地被研发、生产。于是,本文分析了二种情形:一是外资进入东道国初期,由于东道国无法提供最终产品生产所需的核心零部件,同时,外资担忧在东道国当地生产核心零部件会造成较先进技术的流失。因此这个阶段外资往往从国外母公司大量进口核心零部件等中间产品,本文从理论上分析了外资主要从其母国进口中间品的情形,研究表明外资为了避免技术外溢的发生,提升自己的竞争力,在进入东道国的初期,会从海外进口中间产品,在东道国从事非核心部件及最终产品的生产。外资从海外进口核心零部件很大程度上会避免技术外溢的发生,因此在这种条件下,在东道国引进外资的初期,东道国企业生产投入的劳动、资本比例不会发生变化。因此,在外资进入东道国初期,东道国对中间产品的进口是增加的。二是外资进入东道国较长时间后,为了扩大规模,更充分地利用当地资源及优惠政策,会逐步考虑通过设立研发中心等形式在当地开展研发并生产部分核心零部件,同时把一些非核心业务转让给东道国内地企业。这种情形下虽然会产生技术外溢,但是由于外资一直在从事研发活动,所以其对核心技术垄断优势还是存在的。此时,内资企业受技术外溢的影响,生产规模会继续扩大,技术水平会继续提升。因此外资进入东道国较长时间后,随着其研发中心的设立及大量的研发投入,它会在当地生产大量的中间产品,东道国会逐步实现对中间品的进口替代;另一方面,由于技术溢出效应的存在,内资企业生产的产品结构也在升级,这在一定程度上优化了出口结构。最后,论文分析了东道国引进外资和引进技术对出口结构影响的差异。得出的研究结论是:以引进先进技术为主要目的利用外资比以单纯引进外资对一国(主要指发展中国家)出口结构升级的影响要明显得多。换句话说,引进外资的质量比引进外资的数量更加重要,引进外资并不是越多越好,决定国出口商品结构高低的不是利用外资的数量而是引进外资的质量。第三大部分,本文借助2001-2011的分析统计数据,对欧盟FDI对我国进出口商品结构的影响进行实证研究。由于新晋欧盟国家对我国的直接投资数据有限,实证部分仅考虑欧盟原十五国同我国对其出口商品结构的关系。本文借助2001-2011的分析统计数据,在变量选取上,被解释变量为我国对欧盟不同种类技术水平的出口额,即中国对欧盟高技术水平产品出口额,中国对欧盟中高技术水平产品出口额、中国对欧盟中低技术水平产品出口额、中国对欧盟低技术水平产品出口额;选取的解释变量为欧盟对华直接投资额、我国国内生产总值,我国研发与试验发展经费内部支出,欧盟十五国国内生产总值加总额。对上述变量分别进行了时间序列分析和面板数据分析,最后得出研究结论:说明欧盟各国的经济水平是影响我国对其出口的关键因素。每增加一单位EGDP(欧盟国家GDP),出口额增加最多的是中高技术产品,说明随着欧盟各国的经济增长,对我国中高技术产品的需求越高;每增加一单位CGDP(中国GDP),出口额增加最多的是低技术产品,说明我国经济的增长对于低技术产品的促进作用最明显,也反应了我国目前一定程度上还是依赖于资源型、劳动密集型产品的出口。欧盟各国FDI对我国不同类别商品的出口影响,从总体上来看,对中高技术产品和高技术产品的影响比较显著,对中低技术产品和低技术产品的影响较弱。因此,应该继续保持欧盟对华直接投资对中高技术产品出口的促进作用,以中高技术产品的发展慢慢带动高技术产品的研发,进而全面提升我国整体出口商品结构。关于欧盟FDI对我国进口商品结构影响的实证研究由于同样的原因也是仅考虑欧盟原十五国FDI对我国进口商品结构的影响。本文借助2001-2011的分析统计数据,在变量选取上,被解释变量为我国对欧盟不同种类技术水平的进口额,即中国对欧盟高技术水平产品进口额,中国对欧盟中高技术水平产品进口额、中国对欧盟中低技术水平产品进口额、中国对欧盟低技术水平产品进口额;选取的解释变量为欧盟对华直接投资额、我国国内生产总值,我国研发与试验发展经费内部支出,欧盟十五国国内生产总值加总额。对上述变量分别进行了时间序列分析和面板数据分析,最后得出研究结论:欧盟对华FDI同我国对于欧盟的进口具有长期均衡关系,同出口结构不同的是,直接投资对于中高产品的进口从长期看是抑制作用,这与理论分析的结果相吻合,主要是欧盟对华直接投资多投放于制造业,主要生产中高技术产品等,国内的中高技术产业由于欧盟投资的带动和其本地化的研发和生产,逐步完成了进口替代,因此降低了对进口中间产品的要求。实证研究还表明欧盟各国FDI对我国不同类别商品的进口影响,从总体上来看弱于对出口产品的影响,但是影响显著性的排序一致,依次为高技术产品(七个国家)、中高技术产品(五个国家)、中低技术产品(四个国家)、低技术产品(-个国家)。这说明欧盟对华直接投资同样更多地作用于我国中高级技术产品的进口,对我国的进口商品结构同样有显著提升作用。最后根据研究内容,得出研究结论,提出政策建议。

【Abstract】 Trade and investment has been a hot topic in the field of contemporary international trade. In1957, American scholar Robert A.Mundell initially proposed the investment substituting trade model and attention has been paid to the relationship between investment and trade by many scholars since then. Besides the supplement and development of the substituting theory in theoretical circle, the marginal industry expansion theory proposed by Japanese economist K.Kojima(1981) is the most representative theory of trade and investment complementary theories study. This theory suggests that foreign investment can create trade, as well as destroy it. There are also some scholars who find that the relation between investment and trade is uncertain, but this theory does not belong to the mainstream of study. That is to say, theories about the relation between investment and trade can be generalized into two kinds at present:investment substituting trade theory and investment creating trade theory. However, these theories all develops in the direction of the substituting or creating of domestic trade from the investment of developed countries themselves. Since the1980s, the investment of developed countries to developing countries has been on the rise, and developing countries have gradually become the main investment destination of developed countries with the emergence of newly industrialized countries and the rise of developing countries in the world. Particularly, the rapid development of economy caused by China’s utilization of foreign investment has drawn wide attention from scholars at home and abroad. Scholars begin to study the effect of investment from various angles and have got many new achievements. Chinese scholars have made a lot of research from theoretically and empirically to study the impact of foreign direct investment on China’s economy and trade. But these studies mainly concentrate on the influence of world’s direct investment on China’s trade scale and competitiveness, only few scholars have studied the effect of direct investment on China’s trade structureThis paper mainly studies the influence of FDI on China’s trade structure and chooses the influence of EU’s direct investment on China’s trade structure as object. The reason of choosing EU is that, China and EU are all the leading roles of the world economy. Made up of28developed economies, EU is the largest economy and most successful regional economic integration organization in the world by far. China is the world’s fastest growing and largest developing economy. On November21,2013, when meeting European Council President Herman Van Rompuy and European Commission President Jose Manuel Barroso in the Great Hall of the People, Premier Li Keqiang points out in the China-EU cooperation2020strategic planning that:"China-Europe trade and economic relations is one of the world’s largest and most dynamic economic and trade relations. Two-way trade and investment has become the mainspring of Sino-EU respective economic development and innovation. China and EU are shouldering the important responsibility of continuing to pull the world economic growth and realizing common prosperity. Both sides are committed to shaping a innovative, development-linked and interest-integrated world economy and determined to maintain and develop the open world economy. Therefore, based on the spirit of mutual benefit, China and EU are determined to further deepening the trade and investment relations in2020, to promote the open and transparent of the market and make a fair market competition environment. Provide small and medium enterprises with more opportunities." This is also the significance of this paper.Compared to previous studies, this paper would mainly talk about three questions:Firstly, what’s the influence of FDI to the trade structure of the host country? Secondly, what’s the complementarities and difference between the trade structure of China and EU? Thirdly, what’s the influence of EU’s FDI on China’s trade structure?The innovation of this paper is also centered on these three issues:Firstly is to explore and build the theory model towards FDI and the change of host country’s import and export structure, and make theoretical analysis on the influence mechanism of trade structure thus trying to make general theoretical explanation on FDI and the change of host country’s import and export structure. Secondly, using statistical methods to sum up the EU15countries and11new joined members’(without Cyprus whose research materials can’t be found) investment and China’s import and export structure, we researched..contrasted and cleared up the difference and complementarities of the trade between China and EU. Thirdly, we use the data, statistics and the theory models to carry out empirical test.This paper follows the logical structure of literature review---bilateral research status contrast---theory study----empirical study.In the first part, based on the comprehensive literature review and use the OECD, we divide different industries by technological level into high technology industry, middle-high technology industry, middle-low technology industry and low technology industry. In this paper, we put emphasis on the industries that are largely related to the four kinds of industries above and elaborate the development and status of EU’s investment in China and the import and export of products of different technological level Firstly we conclude the change in China and EU’s total amount of import and export since1992. And make analysis on the statistics of the proportion of those four kinds of products according to the original15countries and13newly joined countries, thus knowing the change of China’s structure of import and export with EU objectively and detailedly. On that basis, we make contrast between the status and features of the import and export of China and EU’s original15countries and newly joined12countries. We find that:EU’s original15countries’FDI mainly focuses on manufacturing industry, and the investment in manufacturing industry concentrates on key industries such as capital-intensive industry, the high-tech industry, automobile industry, pharmaceutical and medical device manufacturing industry, electronics and communication manufacturing industry, which are the pillars of the economical development of China. EU’s joint connection of equipment investment and technology export in these industries has become one important source of visual plants and advanced technology of China. Eu’s investment in China has optimized China’s structure of import and export. Due to the difference in economic development and industrial structure, it’s obvious that there are complementarities between China’s and EU’s trade structure. Previously, China’s export to major EU countries mainly focuses on low value-added textile and electrical products such as textile and apparel, shoes, bags, toys, plastic products, coke, tools and steel, and China imports mainly capital goods and high-tech products from these countries with Industrial raw materials, transportation equipment, steel, wheat, primary plastic and medicine ranking second. In recent years, trade of high-tech products is gaining rapid development. Products exported are now gradually converting from low-tech goods and middle low technology products to middle high technology goods and high-tech products, and products imported are still mostly high-tech products and middle high technology goods. EU’s average FDI is well beyond that of Asian countries/areas. EU countries tend to invest in technology-intensive and capital-intensive industries. Therefore, EU countries’ investment will increase China’s domestic capital and bring advanced technology and management experience to China by means of technology transfer and spillovers at the same time, which can improve the production efficiency of local enterprises, promote the upgrade of technology-intensive and capital-intensive industries and accelerate the enterprise transformation in China.In the second part, we study the mechanism of the influence of FDI on the host country’s export commodity structure and have done some empirical research, referring to relevant theory. In this paper, we base on the Dornbush, Fischer and Samuelson (1980) model (DFS model) and have made further expansion. The main difference between the econometric model of this paper and the DFS model is that: the model in this paper is based on the DFS and discusses about the influence of FDI on the import and export structure of the host country and the impact of technology import on host country’s import and export structure respectively. Finally, we compare the difference between the influence of foreign investment and the introduction of technology on the host country’s export structure. Because the statistics study in the third paragraph shows that:The main characteristics of the EU’s direct investment in China’s is that FDI drives the input of advanced technology. That is to say, the introduction of the EU’s direct investment in China has caused the introduction of advanced technology simultaneously. In particular, EU’s original15countries’FDI in China mainly focuses on middle and high technology and they tend to invest in technology-intensive and capital-intensive industries. Therefore, we FDI and carry on variable analysis of FDI and technology progress and construct the theoretical model on change of the FDI and host country’s export trade, based on the reference in the previous research of scholars. Under the condition of opening, we have studied the general influence of FDI on a country’s export structure in two kinds of situations. The first analyzes the impact of the introduction of foreign capital on domestic elements structure, unit cost, comparative advantage and export structure. Its basic conclusion is that:after the introduction of foreign capital, the comparative ratio between labor and capital decreases, relative wages of labor rise, and the cost of capital (interest rate) drops, which results in the country’s reduction of the production scale on these labor-intensive products and getting comparative advantage on the production of these goods. This causes the increase of the kind of domestic superior products and the decrease of foreign superior products. The decrease of foreign superior goods kind may stimulate their research and development of new technology and put it into production area. Therefore, this paper analyzes the second case:foreign country uses new technology in the host country’s production. This case and can be subdivided into two smaller parts, the host country has not acquired new technology and has got two kinds of new technology. And the final conclusion is that:the impact of introduce advanced technology to utilize capital is more obvious than that of simply introduce investment on a country’s (mostly developing countries) import and export structure. In other words, the quality of capital introduction is more important than the quantity. What shapes a country’s export structure is not the quantity of, but the quality of foreign capital introduction. Because the data of the newly joined EU countries’direct investment is limited, the empirical part of this paper only considers the original15countries and the relation of its export commodity structure in our country in order to make further validation of the theory. In this paper, we use the statistics of2001-2011and select the amount of products of different technology level that are exported from China to EU as explained variable. The explanatory variables are EU’s FDI to China, China’s GDP, China’s internal cost of R&D and test and EU15countries’total GDP. We have done time series analysis and panel data analysis on the variables above and drawn the conclusion that:EU countries’economic level is a key element to the export of China to EU. Every unit increase of EGDP promotes the export of middle high technology goods most. It shows that with the economydevelopment, EU countries’demand of China’s middle high technology goods is growing. Every unit increase of CGDP causes the export of China’s low-tech products most. That shows that China’s economy growth promotes the low-tech goods most and China still relies on the export of resources and labor-intensive products to some extent. From the overall, the effect of EU on the export of China’s high-tech and middle high technology products is more obvious, but on middle low technology and low-tech products the effect is weaker. Hence, China should maintain the impact of EU’s promoting effect on the export of China’s high-tech and middle high technology products and drive the R&D of high-tech products by middle high technology products, thus improving China’s export structure comprehensively.In the third part, we have studied the mechanism of the influence of FDI on the host country’s import structure and carried on empirical research. There aren’t theoretical models of the impact of FDI on a country’s import structure by scholars at home and abroad, so the difference between this part and the second part is that, this part only studies the general impact of FDI to a country’s import structure from the perspective of qualitative research due to the limit of the authors’research level and ability. With references to the basic idea of Grossman&Helpman、 Coe&Helpman(1995), Barro and Sala-i-Matin(1995), this article mainly elaborates that the impact of FDI to host country’s import structure is uncertain and it’s under the mutual influence of host country’s economy, foreign technology advantages, domestic research and development capabilities, and other elements. Section2in this part draws on the basic idea of Coe&Helpman (1994)(hereinafter referred to as CH model) the basic idea and carries out empirical tests. Because the limitation of the statistics of EU’s newly joined countries’FDI to China, the empirical part only considers the relation of import structure between China original15countries. In this paper, we use the statistics of2001-2011and select the amount of products of different technology level that are imported to China from EU as explained variable. The explanatory variables are EU’s FDI to China, China’s GDP, China’s internal cost of R&D and test and EU15countries’total GDP. We have made time series analysis and panel data analysis of the above variables respectively and panel data and draw to the conclusion that:There’s a long-term equilibrium between EU’s FDI to China and China’s import from EU. What is different to export structure is that, the FDI can inhibit the import of middle high technology products. Considering EU’s FDI to China mainly focuses on manufacturing industry, especially middle high technology products, we can see it as that the development of China’s middle high technology can satisfy domestic demand and and gradually completed the import substitution, hence reducing the demand for import of those products. Empirical study also shows that the impact of EU’s FDI to different kinds of products of our country. For the overall, it is weaker than the impact on export commodities, but it ranks the same:high-tech products(7countries), middle high technology products(5countries),middle low technology products(4countries),low technology products(1country). This shows that EU’s FDI in China also influences the import of middle high technology products more and can improve the import structure of China. At last, according to the research content, Summed up the research conclusion and give some Suggestions.

  • 【网络出版投稿人】 山东大学
  • 【网络出版年期】2014年 10期
  • 【分类号】F832.6;F752
  • 【被引频次】2
  • 【下载频次】2201
  • 攻读期成果
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