中文摘要：

从汇率、国内吸收以及直接投资与贸易的关系三个角度,利用美国1980-2004年的年度数据,通过简单OLS方法得出美国的进出口方程,可以揭示影响美国贸易逆差的主要原因,以及美元贬值对贸易逆差的影响,结果表明：（1）美元贬值主要通过影响出口而非进口改善贸易收支,但存在2年左右的滞后期,因此美元截至目前的贬值并没有明显改善贸易逆差;（2）从收入影响看,由于H-M收入非对称效应的存在,要减少贸易逆差需要美国相对国外更大幅度的紧缩;（3）从直接投资与贸易的关系看,美国对外直接投资转移了本国的供给,增大了美国进口.大规模减少美国贸易逆差不可能仅仅依靠美元汇率贬值,而是需要中长期的结构性调整, 2006年美国贸易逆差将进一步扩大.

英文摘要：

This paper tries to build a model to explain how exchange rate, domestic and external income, and direct foreign investment have influenced US＇ import and export during 1980 - 2004. Based on OLS simulation of import and export equation, it displays the main causes of US＇s trade deficits and tries to explain why dollar＇s depreciation shows little impact on her deficit improvement. Our conclusion is： 1, Dollar＇s depreciation helps recovering trade balance only with 2 - years delay by improving exports while having little effects on imports, so by now it can hardly reduce US＇ trade deficits extensively. 2, From perspective of income, due to the H - M Income Asymmetry Effects, much contraction is needed in domestic economy than that of abroad to reduce the deficits. 3, The increasing of FDI enlarges the trade deficits. According to our estimation, US＇ trade deficits will expand in 2006. Without a long term structural adjustment, it is hard to expect reducing trade deficits significantly by dollar＇s depreciation alone.