是的，“U”型指的是未知的名义增长率。

Yes, type "U" refers to Unknown for the Nominal Annual Rate.

youdao

但很明显，一旦名义利率下降到零美联储会受约束，因此经济恢复到趋趋向增长率，但不会在金融冲击下恢复所受损失。

But obviously the Fed is constrained once nominal rates hit zero, and so the economy returns to its trend growth rate but never recovers the ground lost during the financial shock.

youdao

假设乏力的GDP增长率在2020年为2.6%，与2010年的2.6%形成对比，名义税率已是4%而非2010年的2.8%，那么美国的债务到2020年上升为GDP的157%。

Assuming anaemic GDP growth of just 1.5% a year as opposed to 2.6%, and a nominal interest rate of 4% rather than 2.8%, us debt rises to 157% of GDP in 2020.

youdao