让我们从一些简单的航空动力学开始，用我的太平洋投资公司（PIMCO）同事格罗斯（Bill Gross）所做的比方来描述美国经济所面临的经济风险。
Let us start with some simple aeronautic dynamics, using an analogy that my PIMCO colleague, Bill Gross, came up with to describe the economic risks facing the American economy.