Robust Counterfactual Predictions in Neoclassical Models of International Trade

经济学家和政策制定者依靠全球经济模型来预测贸易政策的变化，如进口关税，将对生产、工资、就业和消费价格产生影响。这些模型受到限制，以便复制观察到的过去的特征，但研究人员如何准确地施加这些限制是出了名的困难，因此不可避免地存在不确定性和争议。研究人员的目标是通过开发工具来解决这个问题，这些工具使模型和观察到的历史数据之间的联系尽可能简单，因为这些模型通常用于进行预测。因此，经济学家应该能够更有信心地回答有关国际贸易的关键政策问题。考虑到在一般均衡环境中隔离准实验变量所固有的挑战，回答国际贸易中反事实问题的标准方法是依赖计算一般均衡(CGE)模型。这个项目开发了一种使用CGE模型构建稳健的、非参数的反事实预测的新方法。这项研究建立在新古典经济和减少交换经济之间的等价性基础上，在这些经济中，国家只是简单地进行要素服务贸易。这种等价性对于它的简化能力很重要。在减少交换的经济中，竞争均衡可以通过对减少的要素需求系统的分析来完全表征，该系统总结了所有代理人相对于要素服务的偏好。因此，对于一些反事实的问题，如贸易成本统一变化对福利的影响，人们不需要完全了解各国和各行业的需求和生产函数--人们只需要知道来自不同国家的因素之间的替代性。因此，调查人员建议开发工具，并收集新的数据，目的是估计这种可替代性。其中一种方法将依赖于对贸易要素含量的衡量。第二种方法将依赖于使用观察到的数据来构建一般均衡福利变化的最佳非参数界限。

Economists and policy-makers rely on models of the global economy to predict the impact that changes in trade policy, such as import tariffs, will have on production, wages, employment, and consumer prices. These models are constrained so as to replicate features of the observed past, but how exactly a researcher imposes those constraints is notoriously difficult, and hence inevitably uncertain and subject to debate. The investigators aim to address this problem by developing tools that make the connection between model and observed historical data as simple as possible given the predictions that these models are commonly used to make. As a result, economists should be able to answer key policy questions concerning international trade with greater confidence. Given the challenges inherent in isolating quasi-experimental variation in general equilibrium settings, the standard approach to answering counterfactual questions in international trade is to rely on Computational General Equilibrium (CGE) models. This project develops a new way of constructing robust, nonparametric counterfactual predictions using CGE models. This research builds on the equivalence between neoclassical economies and reduced exchange economies in which countries simply trade factor services. This equivalence is important for its simplifying power. In a reduced exchange economy, competitive equilibria can be characterized fully by an analysis of the reduced factor demand system that summarizes all agents' preferences over factor services. Thus, for a number of counterfactual questions, like the welfare impact of uniform changes in trade costs, one does not need the complete knowledge of demand and production functions across countries and industries -- all one needs to know is the substitutability between factors from different countries. The investigators therefore propose to develop tools, and collect new data, aimed at estimating this substitutability. One such approach will rely on measures of the factor content of trade. A second approach will rely on using the observed data to construct the best possible nonparametric bounds on general equilibrium welfare changes.