中国入世与出口增长:关于关税不确定性影响的再检验

China's WTO Accession and Export Growth: A Reexamination of the Role of Tariff Uncertainty Removal

近期一些文献发现以潜在关税上升空间衡量的关税不确定性的下降对中国加入WTO之后的出口有显著的促进作用。本文利用多重差分的方法在更加宽松的回归模型设定下对这一结论的稳健性进行检验。我们发现,在有效控制纺织品和服装出口配额取消的异质性影响之后,关税潜在上升空间的缩减对中国的出口并没有显著影响。我们进一步分析了可能导致这一不显著结果的原因。一方面,有证据显示中国加入WTO之前关于对美出口关税上升的主观概率可能并不高;另一方面,低沉没进入成本也使得进入行为的动态影响有限。由此我们得到结论,中国加入WTO之后的出口增长与不确定性的降低没有关系。这项研究的一个重要启示是,理解不确定性产生的根源对于科学的度量不确定性进而估算其影响至关重要。由此,在衡量贸易争端的影响时也应该对相关经济个体的微观决策机制予以充分考虑。

Some recent studies argue that reduced tariff uncertainty,measured by the shrink of the space of potential increases in tariff,significantly promotes China’s post-WTO export to the U.S.market.This paper reexamines this issue with a multiple difference-in-difference strategy and finds that the impact of tariff uncertainty on China’s export,as claimed in the earlier studies,disappears under a more flexible specification that allows for heterogeneous effects of the elimination of export quotas across countries.With the help of an illustrative model,we further explain how a low likelihood of tariff surge and/or non-substantial sunk costs of entry may account for the absence of impacts and provide supportive evidence.Our major conclusion is that the enormous export growth following China’s entry into WTO cannot be attributed to uncertainty removal.The main takeaway message from the study is that a clear understanding of the nature of policy uncertainty and a carefully constructed measurement are crucial in evaluating its impacts under any context of trade dispute.