政策干预下加入预期因素的汇率变动与贸易余额:一个模型分析

Exchange Rate Changes and Trade Balance by Introducing Expectation Factors under Government Intervention: A Mathematical Analysis

2005年7月人民币汇率制度改革之后,人民币处于长期升值趋势,理论上讲,在满足马歇尔-勒纳的条件下,人民币升值可以矫正我国贸易不均衡的情况,即:我国的贸易顺差应该减少,但是事实上,汇改之后我国对外贸易顺差继续增加。本文假设马歇尔-勒纳条件的前提成立,汇率变动完全(或者部分)传导到贸易品的价格上,在此基础上引入政府干预和消费者预期等因素建立了一个数理模型,对汇率升值与贸易顺差进一步扩大这种特殊现象进行解释。数理模型分析证实:在存在政府干预和消费者预期的条件下,汇率的持续升值会导致贸易顺差进一步扩大(持续贬值导致贸易逆差继续扩大的结论同时成立)。

The long-term tendency of RMB appreciation is established after the reform of RMB exchange rate system in July 2005. Theoretically, in the Marshall-Lerner Condition, the appreciation of RMB can rectify the trade imbalance; that is, China＇s trade surplus should be reduced. But in fact, our foreign trade surplus is continuing to increase after the reform. This paper assumes that the Marshall-Lerner Condition is established, and the exchange rate movements can well transmit to the prices of tradable goods. On this basis, it formulates a model by introducing government intervention, consumer expectation and other factors. This model can explain the particular situation about the currency appreciation and further expanding trade surplus. With it, our analysis has confirmed that the continued appreciation of exchange rate will lead to a further expansion of trade surplus, with the government intervention and consumer expectation in sight.