<正> As an old Chinese saying goes, there is not any ever-lasting banquet under heavens, we could not anticipate an ever-booming U. S. economy. After longtime of robust development, the world's largest economic power, the United States is now suffering from a severe economic slowdown. The gross domestic product(GDP) of the United States contributes almost one-third of the total GDP value of the whole world, the U. S. economic slowdown will drag the growth pace of the world's economy this year. It is not exaggerated to say that "When Uncle Sam catches cold, the