William R. Kerr. 2013. Heterogeneous technology diffusion and Ricardian trade patterns. Working Paper 19657. National Bureau of Economic Research
Abstract: This study tests the importance of Ricardian technology differences for international trade. The empirical analysis has three comparative advantages: including emerging and advanced economies, isolating panel variation regarding the link between productivity and exports, and exploiting heterogeneous technology diffusion from immigrant communities in the United States for identification. The latter instruments are developed By combining panel variation on the development of new technologies across U.S. cities with historical settlement patterns for migrants from countries. The instrumented elasticity of export growth on the intensive margin with respect to the exporter's productivity growth is between 1.6 and 2.4 depending upon weighting.
摘要：本研究检验了李嘉图技术差异在国际贸易中的重要性。这个实证分析有三大比较优势：囊括了新兴的与发达的经济，隔离了关于生产力与出口间的关联的面板差异，并利用来自美国移民社区的异质性技术传播来进行鉴定。将美国城市的新技术发展的面板差异与来自不同国家移民的历史聚落模式相结合，我们开发出了后面的工具。依据不同的权重，出口增长的集约边际对出口国生产力增长的弹性在1.6到2.4之间。
数据来源：
· Labor Productivity Data——United Nations Industrial Development Organization (UNIDO)
·Export Volumes——1975-2000 World Trade Flows Database (WTF)
·US Historical Settlement Patterns——1980 Census of Populations
·US Patenting Data——United States Patent and Trademark Office (USPTO) from January 1975 to May 2009.
研究方法：OLS最小二乘法；加入工具变量
Conclusion: While the principle of Ricardian technology differences as a source of trade is well established in the theory of international economics, empirical evaluations of its importance are relatively rare due to the difficulty of quantifying and isolating technology differences. This study exploits heterogeneous technology diffusion from the United States through ethnic migrant networks to make additional headway. Estimations find bilateral manufacturing exports respond positively to growth in observable measures of comparative advantages. Ricardian technology differences are an important determinant of trade in longitudinal changes, in addition to their cross-sectional role discussed earlier.
Leamer and Levinsohn (1994) argue that trade models should be taken with a grain of salt and applied in contexts for which they are appropriate. This is certainly true when interpreting these results. The estimating frameworks have specially sought to remove trade resulting from factor endowments, increasing returns, consumer preferences, etc. rather than test against them. Moreover, manufacturing exports are likely more sensitive to patentable technology improvements than the average sector, and the empirical reach of the constructed dataset to include emerging economies like China and India heightens this sensitivity. Further research is needed to generalize technology’s role to a broader set of industrial sectors and environments.
Beyond quantifying the link between technology and trade for manufacturing, this paper also serves as input into research regarding the benefits and costs of emigration to the United States for the migrants’ home countries (i.e., the "brain drain" or "brain gain" debate). While focusing on the Ricardian model and its parameters, the paper establishes that the technology transfer from overseas migrants are strong enough to meaningfully promote exports. Care should be taken to not overly interpret these findings as strong evidence of a big gain from migration.
The paper does not seek to establish a clear counterfactual in the context of immigration from the source countries’ point of view (e.g., Agrawal et al. 2011). As such, the positive export elasticities due to US heterogeneous technology diffusion do not constitute welfare statements relative to other scenarios. Future research needs to examine these welfare implications further.
结论：虽然李嘉图技术差异原理作为贸易的一种来源在国际经济学理论中已经非常完善，但由于在量化和隔离技术差异上的困难，对于其重要性的实证评估相对较少。本研究利用来自美国的异质化技术传播，通过种族迁移网络去获得进一步的成果。研究发现双边的制造业出口对可观察到的比较优势的测量有着积极的反应。李嘉图技术差异不仅是先前讨论过的横截面角色的决定因素，更是经度变化中的交易的重要决定因素。
Leamer 与 Levinsohn (1994)主张贸易模型应当被有保留地接受，并仅在适合的条件下应用。这是在解释这些结果时理所当然的。这个估测框架移除由要素禀赋、递增收益消费者偏好等因素导致的贸易，而非再检验它们。更重要的是，制造业出口相对于其他部门，似乎对专利技术提升非常敏感，且这种涵盖了以中国和印度为代表的新兴经济的结构化资料组的实证范围提高了该敏感度。我们需要进一步的研究去概括技术在更广阔的工业部门与环境背景中的角色。
在量化制造业技术与贸易间的联系之外，这篇论文同时也可以作为输入用于研究移民美国对于迁移者祖国的成本和收益（即“人才流失”或“人才引进”的争论）。在关注李嘉图模型与其系数的同时，这篇论文还指出，海外迁移者带来的技术是足够强力的，它能够有意义地促进出口。我们不应当过度地解读这些发现，将他们视为移民能够带来巨大好处的强力证据。
这篇论文并非为了从移民源国家的视角提出关于移民的清晰的反事实(例如 Agrawal等人. 2011)。如此，由于美国异质化技术传播带来的积极的出口弹性不构成对于其他情景的福利声明。未来的研究需要进一步检验这种福利的含义。
（By 潘一坤) |
