贸易受益与汇率

Gains of Trade and Exchange Rates

多数教科书的相关理论都暗含着这样一个假设：汇率决定贸易受益的分配，而不是贸易受益的绝对水平。由于汇率不影响一国的相对价格，因此贸易结构和相应的贸易受益也不受影响。然而，汇率确实影响贸易条件和受益的分配，但相反却是中性的。本文将运用一个简单的两国、两种商品模型来说明贸易受益的分配（以国内货币计算）取决于发起贸易的国家。如果没有一个国家发起贸易，那么贸易受益则只意味着汇率。考虑到货币可兑换性，贸易结构将潜在地受到影响，货币的流动可能充当第三种“转移”商品的作用。由于外国货币都有一定的国内价值，在贸易框架内它就成为第三种商品，贸易受益就可能超过简单的两种商品、两个国家的情况。有趣的是，在货币可兑换的情况下，两种商品模型中的隐形汇率和双边贸易是不一致的。最后，本文认为文中建立的简单模型说明了汇率并不能平衡通货（或转移商品）的流动，同时仍然保留着可兑换性。

An implicit assumption in most textbooks is that exchange rates determine the distribution of the gains from trade but not the absolute level of gains from trade. Because exchange rates do not affect relative prices within a country, the pattern of trade and the corresponding gains of trade are also unaffected. The exchange rate does, however, affect the terms of trade and the distribution of gains, but is otherwise neutral. Here we use a simple two-commodity, two-coun- try model with non-convertible currencies to demonstrate that assignment of the gains of trade （measured in domestic currency） depends upon the country initiating trade. If either country can initiate trade, then the gains of trade imply a unique exchange rate. With the introduction of convertibility, the pattern of trade is potentially affected and currency flows may act as a third ＂transfer＂ commodity. Since foreign currency has a specific domestic value, it becomes a third commodity within the trade framework and the gains from trade have the potential to increase beyond that which would take place in a simple two-commodity two-country case. Interestingly, with currency convertibility, the implicit rate of exchange from the two-com- modity model is inconsistent with bi-lateral trade. Finally, we believe our simple model demonstrates that there is no exchange rate capable of balancing currency （or transfer commodity） flows and at the same time still preserving convertibility.