Collaborative Research: Intertemporal Trade

在过去的半个世纪里，世界经济在许多方面变得更加一体化：国际贸易的增长速度远远快于世界产出。外国资产在投资组合中所占份额越来越大。各国更多地依赖国际储蓄来为投资和政府赤字融资。由于进出口数据很容易获得，可以在静态框架中进行分析，因此对第一种形式的整合进行了最深入的分析。在以前的工作中，研究人员开发了一个国际贸易的定量一般均衡模型，该模型可以包含有关单个国家的大量细节以及将它们分开的地理障碍。由于涉及到复杂的动态因素，对金融一体化的研究仍然非常原始。模型只有两三个国家的代表性是非常程式化的。因此，它们无法整合数据中显示的丰富多样性。这项研究建立了一个丰富的多国动态框架，将时间整合到静态框架中，调查人员在他们以前的工作。这项研究有三个组成部分。第一个模型将贸易失衡纳入其中，以评估经常账户逆转对国家内部和国家之间的汇率、福利和收入分配的影响。该研究解决的一个关键政策问题是，美国经常账户赤字可能出现的逆转将对美国和海外产生何种影响。结果反映了（i）贸易商品的调整（广泛的利润率），（ii）劳动力和其他生产要素在贸易和非贸易活动之间的流动性，以及（iii）地理在调整中的作用。由于调整能力有限，各国实现经常账户再平衡所带来的相对GDP变化很大。由于不可贸易性的普遍存在，汇率变化对生活水平的影响较为温和。第二部分介绍了跨期最大化。静态框架被扩展到考虑到不同时间和不同国家的要素禀赋、技术和贸易壁垒的差异。各国进行跨期贸易以适应冲击。但是，就地理壁垒所吸收的资源而言，这种贸易是昂贵的。计算表明，静态引力模型所暗示的贸易壁垒规模阻碍了消费平滑，其数量与数据中观察到的一致。第三部分考察投资和消费。结果表明，地理障碍可以解释储蓄和投资的高相关性（但下降）。分析使人们更深入地了解各国贸易平衡长期波动的决定因素和后果。这项研究进一步提高了经济学家对一个动态的多国世界进行定量建模的能力。它连接了两个文献，贸易流量的静态建模和动态开放经济宏观经济学。它所发展的框架可用于解决国际经济政策中的一系列关键问题。

Over the last half century the world economy has become more integrated in a number of dimensions: International trade has grown much faster than world output. Foreign assets constitute a growing share of portfolios. Countries rely more on international pools of saving to finance investment and government deficits. Because data on imports and exports are readily available and can be analyzed in a static framework, the first form of integration has been analyzed in greatest depth. In previous work the investigators developed a quantitative general equilibrium model of international trade that can incorporate substantial detail about individual countries and the geographic barriers that separate them. Because complex dynamic considerations are involved, investigation into financial integration remains much more primitive. Models have only two or three countries whose representation is very stylized. Hence they are incapable of incorporating the rich variety displayed in the data. This research builds a rich multicountry dynamic framework that integrates time into the static framework that the investigators developed in their previous work. The research has three components. The first incorporates trade imbalances to assess the impact of current account reversals on exchange rates, welfare, and income distribution within and across countries. A key policy question that the research addresses is the impact that a likely reversal of the U.S. current account deficit will have in the United States and abroad. The outcome reflects (i) adjustment in the set of goods that are traded (the extensive margin), (ii) the mobility of labor and other factors of production between traded and nontraded activities, and (iii) the role of geography in adjustment. With little ability to adjust, the relative GDP changes across countries associated with achieving current account rebalancing are large. Because of the pervasiveness of nontradability, the effect of exchange rate changes on standards of living is more modest. The second component introduces intertemporal maximization. The static framework is extended to allow for differences in factor endowments, technology, and trade barriers over time as well as across countries. Countries trade intertemporally to accommodate shocks. But this trade is costly in terms of the resources absorbed by geographic barriers. Calculations indicate that trade barriers of the magnitude implied by static gravity models impede consumption smoothing by amounts consistent with that observed in the data. The third component examines investment as well as consumption. Results indicate that geographic barriers can explain the high (but declining) correlation of savings and investment. The analysis provides a deeper understanding of the determinants and consequences of long-run swings in countries' trade balances. This research furthers economists' ability to model quantitatively a dynamic, multi-country world. It connects two literatures, the static modeling of trade flows and dynamic open-economy macroeconomics. The framework it develops can be used to address a host of key issues in international economic policy.