经常项目动态路径与美元长期贬值态势

The Dynamic Path of Current Account and Long-Term Depreciation Trend for the US Dollar

运用资产跨国组合模型说明,巨额对外净债务使美元呈现长期贬值态势。美国巨额对外净债务是20世纪80年代以来持续经常项目赤字累积的结果,因此,必须削减经常项目赤字才能降低净债务头寸。而经常项目赤字动态收敛的速度取决于资产收益率、汇率贬值的弹性值和汇率。资产收益率越低,弹性值越大,收敛速度越快。由于金融市场的反应速度快于商品市场,汇率贬值首先会降低经常项目赤字的收敛速度,然后会加大收敛速度。

Based on portfolio model, this paper explored the causes of the huge net external debt position and there existed long-run depreciation trend for the US dollar. The US huge net external debt position derived from durative current account deficits since 1980s. So, the US must reduce the huge current account deficits before they can reduce the net external debt position. The dynamic convergence rate of current account deficits determined by the gross rate of return on US assets, trade elasticity value for exchange rate depreciation, the US dollar exchange rate. The lower the gross rate of return on US assets is, the larger the trade elasticity value is , then the sooner the dynamic convergence rate of current account deficits is. However, after the US dollar depreciation, the dynamic convergence rate of current account deficits falls firstly, and accelerates subsequently because financial market＇s response to price information is sooner than goods market＇ s.